<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html lang="en">
<head>
<title>Source code</title>
<link rel="stylesheet" type="text/css" href="../../../../../../stylesheet.css" title="Style">
</head>
<body>
<div class="sourceContainer">
<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2011 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.util.concurrent;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import com.google.common.annotations.Beta;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import com.google.common.annotations.VisibleForTesting;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import com.google.common.base.Function;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.base.Preconditions;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import com.google.common.collect.ImmutableSet;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import com.google.common.collect.Lists;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import com.google.common.collect.MapMaker;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import com.google.common.collect.Maps;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import com.google.common.collect.Sets;<a name="line.29"></a>
<span class="sourceLineNo">030</span><a name="line.30"></a>
<span class="sourceLineNo">031</span>import java.util.ArrayList;<a name="line.31"></a>
<span class="sourceLineNo">032</span>import java.util.Arrays;<a name="line.32"></a>
<span class="sourceLineNo">033</span>import java.util.Collections;<a name="line.33"></a>
<span class="sourceLineNo">034</span>import java.util.EnumMap;<a name="line.34"></a>
<span class="sourceLineNo">035</span>import java.util.List;<a name="line.35"></a>
<span class="sourceLineNo">036</span>import java.util.Map;<a name="line.36"></a>
<span class="sourceLineNo">037</span>import java.util.Set;<a name="line.37"></a>
<span class="sourceLineNo">038</span>import java.util.concurrent.TimeUnit;<a name="line.38"></a>
<span class="sourceLineNo">039</span>import java.util.concurrent.locks.ReentrantLock;<a name="line.39"></a>
<span class="sourceLineNo">040</span>import java.util.concurrent.locks.ReentrantReadWriteLock;<a name="line.40"></a>
<span class="sourceLineNo">041</span>import java.util.logging.Level;<a name="line.41"></a>
<span class="sourceLineNo">042</span>import java.util.logging.Logger;<a name="line.42"></a>
<span class="sourceLineNo">043</span><a name="line.43"></a>
<span class="sourceLineNo">044</span>import javax.annotation.Nullable;<a name="line.44"></a>
<span class="sourceLineNo">045</span>import javax.annotation.concurrent.ThreadSafe;<a name="line.45"></a>
<span class="sourceLineNo">046</span><a name="line.46"></a>
<span class="sourceLineNo">047</span>/**<a name="line.47"></a>
<span class="sourceLineNo">048</span> * The {@code CycleDetectingLockFactory} creates {@link ReentrantLock} instances and<a name="line.48"></a>
<span class="sourceLineNo">049</span> * {@link ReentrantReadWriteLock} instances that detect potential deadlock by checking<a name="line.49"></a>
<span class="sourceLineNo">050</span> * for cycles in lock acquisition order.<a name="line.50"></a>
<span class="sourceLineNo">051</span> * &lt;p&gt;<a name="line.51"></a>
<span class="sourceLineNo">052</span> * Potential deadlocks detected when calling the {@code lock()},<a name="line.52"></a>
<span class="sourceLineNo">053</span> * {@code lockInterruptibly()}, or {@code tryLock()} methods will result in the<a name="line.53"></a>
<span class="sourceLineNo">054</span> * execution of the {@link Policy} specified when creating the factory. The<a name="line.54"></a>
<span class="sourceLineNo">055</span> * currently available policies are:<a name="line.55"></a>
<span class="sourceLineNo">056</span> * &lt;ul&gt;<a name="line.56"></a>
<span class="sourceLineNo">057</span> * &lt;li&gt;DISABLED<a name="line.57"></a>
<span class="sourceLineNo">058</span> * &lt;li&gt;WARN<a name="line.58"></a>
<span class="sourceLineNo">059</span> * &lt;li&gt;THROW<a name="line.59"></a>
<span class="sourceLineNo">060</span> * &lt;/ul&gt;<a name="line.60"></a>
<span class="sourceLineNo">061</span> * The locks created by a factory instance will detect lock acquisition cycles<a name="line.61"></a>
<span class="sourceLineNo">062</span> * with locks created by other {@code CycleDetectingLockFactory} instances<a name="line.62"></a>
<span class="sourceLineNo">063</span> * (except those with {@code Policy.DISABLED}). A lock's behavior when a cycle<a name="line.63"></a>
<span class="sourceLineNo">064</span> * is detected, however, is defined by the {@code Policy} of the factory that<a name="line.64"></a>
<span class="sourceLineNo">065</span> * created it. This allows detection of cycles across components while<a name="line.65"></a>
<span class="sourceLineNo">066</span> * delegating control over lock behavior to individual components.<a name="line.66"></a>
<span class="sourceLineNo">067</span> * &lt;p&gt;<a name="line.67"></a>
<span class="sourceLineNo">068</span> * Applications are encouraged to use a {@code CycleDetectingLockFactory} to<a name="line.68"></a>
<span class="sourceLineNo">069</span> * create any locks for which external/unmanaged code is executed while the lock<a name="line.69"></a>
<span class="sourceLineNo">070</span> * is held. (See caveats under &lt;strong&gt;Performance&lt;/strong&gt;).<a name="line.70"></a>
<span class="sourceLineNo">071</span> * &lt;p&gt;<a name="line.71"></a>
<span class="sourceLineNo">072</span> * &lt;strong&gt;Cycle Detection&lt;/strong&gt;<a name="line.72"></a>
<span class="sourceLineNo">073</span> * &lt;p&gt;<a name="line.73"></a>
<span class="sourceLineNo">074</span> * Deadlocks can arise when locks are acquired in an order that forms a cycle.<a name="line.74"></a>
<span class="sourceLineNo">075</span> * In a simple example involving two locks and two threads, deadlock occurs<a name="line.75"></a>
<span class="sourceLineNo">076</span> * when one thread acquires Lock A, and then Lock B, while another thread<a name="line.76"></a>
<span class="sourceLineNo">077</span> * acquires Lock B, and then Lock A:<a name="line.77"></a>
<span class="sourceLineNo">078</span> * &lt;pre&gt;<a name="line.78"></a>
<span class="sourceLineNo">079</span> * Thread1: acquire(LockA) --X acquire(LockB)<a name="line.79"></a>
<span class="sourceLineNo">080</span> * Thread2: acquire(LockB) --X acquire(LockA)<a name="line.80"></a>
<span class="sourceLineNo">081</span> * &lt;/pre&gt;<a name="line.81"></a>
<span class="sourceLineNo">082</span> * Neither thread will progress because each is waiting for the other. In more<a name="line.82"></a>
<span class="sourceLineNo">083</span> * complex applications, cycles can arise from interactions among more than 2<a name="line.83"></a>
<span class="sourceLineNo">084</span> * locks:<a name="line.84"></a>
<span class="sourceLineNo">085</span> * &lt;pre&gt;<a name="line.85"></a>
<span class="sourceLineNo">086</span> * Thread1: acquire(LockA) --X acquire(LockB)<a name="line.86"></a>
<span class="sourceLineNo">087</span> * Thread2: acquire(LockB) --X acquire(LockC)<a name="line.87"></a>
<span class="sourceLineNo">088</span> * ...<a name="line.88"></a>
<span class="sourceLineNo">089</span> * ThreadN: acquire(LockN) --X acquire(LockA)<a name="line.89"></a>
<span class="sourceLineNo">090</span> * &lt;/pre&gt;<a name="line.90"></a>
<span class="sourceLineNo">091</span> * The implementation detects cycles by constructing a directed graph in which<a name="line.91"></a>
<span class="sourceLineNo">092</span> * each lock represents a node and each edge represents an acquisition ordering<a name="line.92"></a>
<span class="sourceLineNo">093</span> * between two locks.<a name="line.93"></a>
<span class="sourceLineNo">094</span> * &lt;ul&gt;<a name="line.94"></a>
<span class="sourceLineNo">095</span> * &lt;li&gt;Each lock adds (and removes) itself to/from a ThreadLocal Set of acquired<a name="line.95"></a>
<span class="sourceLineNo">096</span> *   locks when the Thread acquires its first hold (and releases its last<a name="line.96"></a>
<span class="sourceLineNo">097</span> *   remaining hold).<a name="line.97"></a>
<span class="sourceLineNo">098</span> * &lt;li&gt;Before the lock is acquired, the lock is checked against the current set<a name="line.98"></a>
<span class="sourceLineNo">099</span> *   of acquired locks---to each of the acquired locks, an edge from the<a name="line.99"></a>
<span class="sourceLineNo">100</span> *   soon-to-be-acquired lock is either verified or created.<a name="line.100"></a>
<span class="sourceLineNo">101</span> * &lt;li&gt;If a new edge needs to be created, the outgoing edges of the acquired<a name="line.101"></a>
<span class="sourceLineNo">102</span> *   locks are traversed to check for a cycle that reaches the lock to be<a name="line.102"></a>
<span class="sourceLineNo">103</span> *   acquired. If no cycle is detected, a new "safe" edge is created.<a name="line.103"></a>
<span class="sourceLineNo">104</span> * &lt;li&gt;If a cycle is detected, an "unsafe" (cyclic) edge is created to represent<a name="line.104"></a>
<span class="sourceLineNo">105</span> *   a potential deadlock situation, and the appropriate Policy is executed.<a name="line.105"></a>
<span class="sourceLineNo">106</span> * &lt;/ul&gt;<a name="line.106"></a>
<span class="sourceLineNo">107</span> * Note that detection of potential deadlock does not necessarily indicate that<a name="line.107"></a>
<span class="sourceLineNo">108</span> * deadlock will happen, as it is possible that higher level application logic<a name="line.108"></a>
<span class="sourceLineNo">109</span> * prevents the cyclic lock acquisition from occurring. One example of a false<a name="line.109"></a>
<span class="sourceLineNo">110</span> * positive is:<a name="line.110"></a>
<span class="sourceLineNo">111</span> * &lt;pre&gt;<a name="line.111"></a>
<span class="sourceLineNo">112</span> * LockA -&amp;gt; LockB -&amp;gt; LockC<a name="line.112"></a>
<span class="sourceLineNo">113</span> * LockA -&amp;gt; LockC -&amp;gt; LockB<a name="line.113"></a>
<span class="sourceLineNo">114</span> * &lt;/pre&gt;<a name="line.114"></a>
<span class="sourceLineNo">115</span> *<a name="line.115"></a>
<span class="sourceLineNo">116</span> * &lt;strong&gt;ReadWriteLocks&lt;/strong&gt;<a name="line.116"></a>
<span class="sourceLineNo">117</span> * &lt;p&gt;<a name="line.117"></a>
<span class="sourceLineNo">118</span> * While {@code ReadWriteLock} instances have different properties and can form cycles<a name="line.118"></a>
<span class="sourceLineNo">119</span> * without potential deadlock, this class treats {@code ReadWriteLock} instances as<a name="line.119"></a>
<span class="sourceLineNo">120</span> * equivalent to traditional exclusive locks. Although this increases the false<a name="line.120"></a>
<span class="sourceLineNo">121</span> * positives that the locks detect (i.e. cycles that will not actually result in<a name="line.121"></a>
<span class="sourceLineNo">122</span> * deadlock), it simplifies the algorithm and implementation considerably. The<a name="line.122"></a>
<span class="sourceLineNo">123</span> * assumption is that a user of this factory wishes to eliminate any cyclic<a name="line.123"></a>
<span class="sourceLineNo">124</span> * acquisition ordering.<a name="line.124"></a>
<span class="sourceLineNo">125</span> * &lt;p&gt;<a name="line.125"></a>
<span class="sourceLineNo">126</span> * &lt;strong&gt;Explicit Lock Acquisition Ordering&lt;/strong&gt;<a name="line.126"></a>
<span class="sourceLineNo">127</span> * &lt;p&gt;<a name="line.127"></a>
<span class="sourceLineNo">128</span> * The {@link CycleDetectingLockFactory.WithExplicitOrdering} class can be used<a name="line.128"></a>
<span class="sourceLineNo">129</span> * to enforce an application-specific ordering in addition to performing general<a name="line.129"></a>
<span class="sourceLineNo">130</span> * cycle detection.<a name="line.130"></a>
<span class="sourceLineNo">131</span> * &lt;p&gt;<a name="line.131"></a>
<span class="sourceLineNo">132</span> * &lt;strong&gt;Garbage Collection&lt;/strong&gt;<a name="line.132"></a>
<span class="sourceLineNo">133</span> * &lt;p&gt;<a name="line.133"></a>
<span class="sourceLineNo">134</span> * In order to allow proper garbage collection of unused locks, the edges of<a name="line.134"></a>
<span class="sourceLineNo">135</span> * the lock graph are weak references.<a name="line.135"></a>
<span class="sourceLineNo">136</span> * &lt;p&gt;<a name="line.136"></a>
<span class="sourceLineNo">137</span> * &lt;strong&gt;Performance&lt;/strong&gt;<a name="line.137"></a>
<span class="sourceLineNo">138</span> * &lt;p&gt;<a name="line.138"></a>
<span class="sourceLineNo">139</span> * The extra bookkeeping done by cycle detecting locks comes at some cost to<a name="line.139"></a>
<span class="sourceLineNo">140</span> * performance. Benchmarks (as of December 2011) show that:<a name="line.140"></a>
<span class="sourceLineNo">141</span> *<a name="line.141"></a>
<span class="sourceLineNo">142</span> * &lt;ul&gt;<a name="line.142"></a>
<span class="sourceLineNo">143</span> * &lt;li&gt;for an unnested {@code lock()} and {@code unlock()}, a cycle detecting<a name="line.143"></a>
<span class="sourceLineNo">144</span> *   lock takes 38ns as opposed to the 24ns taken by a plain lock.<a name="line.144"></a>
<span class="sourceLineNo">145</span> * &lt;li&gt;for nested locking, the cost increases with the depth of the nesting:<a name="line.145"></a>
<span class="sourceLineNo">146</span> *   &lt;ul&gt;<a name="line.146"></a>
<span class="sourceLineNo">147</span> *   &lt;li&gt; 2 levels: average of 64ns per lock()/unlock()<a name="line.147"></a>
<span class="sourceLineNo">148</span> *   &lt;li&gt; 3 levels: average of 77ns per lock()/unlock()<a name="line.148"></a>
<span class="sourceLineNo">149</span> *   &lt;li&gt; 4 levels: average of 99ns per lock()/unlock()<a name="line.149"></a>
<span class="sourceLineNo">150</span> *   &lt;li&gt; 5 levels: average of 103ns per lock()/unlock()<a name="line.150"></a>
<span class="sourceLineNo">151</span> *   &lt;li&gt;10 levels: average of 184ns per lock()/unlock()<a name="line.151"></a>
<span class="sourceLineNo">152</span> *   &lt;li&gt;20 levels: average of 393ns per lock()/unlock()<a name="line.152"></a>
<span class="sourceLineNo">153</span> *   &lt;/ul&gt;<a name="line.153"></a>
<span class="sourceLineNo">154</span> * &lt;/ul&gt;<a name="line.154"></a>
<span class="sourceLineNo">155</span> *<a name="line.155"></a>
<span class="sourceLineNo">156</span> * As such, the CycleDetectingLockFactory may not be suitable for<a name="line.156"></a>
<span class="sourceLineNo">157</span> * performance-critical applications which involve tightly-looped or<a name="line.157"></a>
<span class="sourceLineNo">158</span> * deeply-nested locking algorithms.<a name="line.158"></a>
<span class="sourceLineNo">159</span> *<a name="line.159"></a>
<span class="sourceLineNo">160</span> * @author Darick Tong<a name="line.160"></a>
<span class="sourceLineNo">161</span> * @since 13.0<a name="line.161"></a>
<span class="sourceLineNo">162</span> */<a name="line.162"></a>
<span class="sourceLineNo">163</span>@Beta<a name="line.163"></a>
<span class="sourceLineNo">164</span>@ThreadSafe<a name="line.164"></a>
<span class="sourceLineNo">165</span>public class CycleDetectingLockFactory {<a name="line.165"></a>
<span class="sourceLineNo">166</span><a name="line.166"></a>
<span class="sourceLineNo">167</span>  /**<a name="line.167"></a>
<span class="sourceLineNo">168</span>   * Encapsulates the action to be taken when a potential deadlock is<a name="line.168"></a>
<span class="sourceLineNo">169</span>   * encountered. Clients can use one of the predefined {@link Policies} or<a name="line.169"></a>
<span class="sourceLineNo">170</span>   * specify a custom implementation. Implementations must be thread-safe.<a name="line.170"></a>
<span class="sourceLineNo">171</span>   *<a name="line.171"></a>
<span class="sourceLineNo">172</span>   * @since 13.0<a name="line.172"></a>
<span class="sourceLineNo">173</span>   */<a name="line.173"></a>
<span class="sourceLineNo">174</span>  @Beta<a name="line.174"></a>
<span class="sourceLineNo">175</span>  @ThreadSafe<a name="line.175"></a>
<span class="sourceLineNo">176</span>  public interface Policy {<a name="line.176"></a>
<span class="sourceLineNo">177</span><a name="line.177"></a>
<span class="sourceLineNo">178</span>    /**<a name="line.178"></a>
<span class="sourceLineNo">179</span>     * Called when a potential deadlock is encountered. Implementations can<a name="line.179"></a>
<span class="sourceLineNo">180</span>     * throw the given {@code exception} and/or execute other desired logic.<a name="line.180"></a>
<span class="sourceLineNo">181</span>     * &lt;p&gt;<a name="line.181"></a>
<span class="sourceLineNo">182</span>     * Note that the method will be called even upon an invocation of<a name="line.182"></a>
<span class="sourceLineNo">183</span>     * {@code tryLock()}. Although {@code tryLock()} technically recovers from<a name="line.183"></a>
<span class="sourceLineNo">184</span>     * deadlock by eventually timing out, this behavior is chosen based on the<a name="line.184"></a>
<span class="sourceLineNo">185</span>     * assumption that it is the application's wish to prohibit any cyclical<a name="line.185"></a>
<span class="sourceLineNo">186</span>     * lock acquisitions.<a name="line.186"></a>
<span class="sourceLineNo">187</span>     */<a name="line.187"></a>
<span class="sourceLineNo">188</span>    void handlePotentialDeadlock(PotentialDeadlockException exception);<a name="line.188"></a>
<span class="sourceLineNo">189</span>  }<a name="line.189"></a>
<span class="sourceLineNo">190</span><a name="line.190"></a>
<span class="sourceLineNo">191</span>  /**<a name="line.191"></a>
<span class="sourceLineNo">192</span>   * Pre-defined {@link Policy} implementations.<a name="line.192"></a>
<span class="sourceLineNo">193</span>   *<a name="line.193"></a>
<span class="sourceLineNo">194</span>   * @since 13.0<a name="line.194"></a>
<span class="sourceLineNo">195</span>   */<a name="line.195"></a>
<span class="sourceLineNo">196</span>  @Beta<a name="line.196"></a>
<span class="sourceLineNo">197</span>  public enum Policies implements Policy {<a name="line.197"></a>
<span class="sourceLineNo">198</span>    /**<a name="line.198"></a>
<span class="sourceLineNo">199</span>     * When potential deadlock is detected, this policy results in the throwing<a name="line.199"></a>
<span class="sourceLineNo">200</span>     * of the {@code PotentialDeadlockException} indicating the potential<a name="line.200"></a>
<span class="sourceLineNo">201</span>     * deadlock, which includes stack traces illustrating the cycle in lock<a name="line.201"></a>
<span class="sourceLineNo">202</span>     * acquisition order.<a name="line.202"></a>
<span class="sourceLineNo">203</span>     */<a name="line.203"></a>
<span class="sourceLineNo">204</span>    THROW {<a name="line.204"></a>
<span class="sourceLineNo">205</span>      @Override<a name="line.205"></a>
<span class="sourceLineNo">206</span>      public void handlePotentialDeadlock(PotentialDeadlockException e) {<a name="line.206"></a>
<span class="sourceLineNo">207</span>        throw e;<a name="line.207"></a>
<span class="sourceLineNo">208</span>      }<a name="line.208"></a>
<span class="sourceLineNo">209</span>    },<a name="line.209"></a>
<span class="sourceLineNo">210</span><a name="line.210"></a>
<span class="sourceLineNo">211</span>    /**<a name="line.211"></a>
<span class="sourceLineNo">212</span>     * When potential deadlock is detected, this policy results in the logging<a name="line.212"></a>
<span class="sourceLineNo">213</span>     * of a {@link Level#SEVERE} message indicating the potential deadlock,<a name="line.213"></a>
<span class="sourceLineNo">214</span>     * which includes stack traces illustrating the cycle in lock acquisition<a name="line.214"></a>
<span class="sourceLineNo">215</span>     * order.<a name="line.215"></a>
<span class="sourceLineNo">216</span>     */<a name="line.216"></a>
<span class="sourceLineNo">217</span>    WARN {<a name="line.217"></a>
<span class="sourceLineNo">218</span>      @Override<a name="line.218"></a>
<span class="sourceLineNo">219</span>      public void handlePotentialDeadlock(PotentialDeadlockException e) {<a name="line.219"></a>
<span class="sourceLineNo">220</span>        logger.log(Level.SEVERE, "Detected potential deadlock", e);<a name="line.220"></a>
<span class="sourceLineNo">221</span>      }<a name="line.221"></a>
<span class="sourceLineNo">222</span>    },<a name="line.222"></a>
<span class="sourceLineNo">223</span><a name="line.223"></a>
<span class="sourceLineNo">224</span>    /**<a name="line.224"></a>
<span class="sourceLineNo">225</span>     * Disables cycle detection. This option causes the factory to return<a name="line.225"></a>
<span class="sourceLineNo">226</span>     * unmodified lock implementations provided by the JDK, and is provided to<a name="line.226"></a>
<span class="sourceLineNo">227</span>     * allow applications to easily parameterize when cycle detection is<a name="line.227"></a>
<span class="sourceLineNo">228</span>     * enabled.<a name="line.228"></a>
<span class="sourceLineNo">229</span>     * &lt;p&gt;<a name="line.229"></a>
<span class="sourceLineNo">230</span>     * Note that locks created by a factory with this policy will &lt;em&gt;not&lt;/em&gt;<a name="line.230"></a>
<span class="sourceLineNo">231</span>     * participate the cycle detection performed by locks created by other<a name="line.231"></a>
<span class="sourceLineNo">232</span>     * factories.<a name="line.232"></a>
<span class="sourceLineNo">233</span>     */<a name="line.233"></a>
<span class="sourceLineNo">234</span>    DISABLED {<a name="line.234"></a>
<span class="sourceLineNo">235</span>      @Override<a name="line.235"></a>
<span class="sourceLineNo">236</span>      public void handlePotentialDeadlock(PotentialDeadlockException e) {<a name="line.236"></a>
<span class="sourceLineNo">237</span>      }<a name="line.237"></a>
<span class="sourceLineNo">238</span>    };<a name="line.238"></a>
<span class="sourceLineNo">239</span>  }<a name="line.239"></a>
<span class="sourceLineNo">240</span><a name="line.240"></a>
<span class="sourceLineNo">241</span>  /**<a name="line.241"></a>
<span class="sourceLineNo">242</span>   * Creates a new factory with the specified policy.<a name="line.242"></a>
<span class="sourceLineNo">243</span>   */<a name="line.243"></a>
<span class="sourceLineNo">244</span>  public static CycleDetectingLockFactory newInstance(Policy policy) {<a name="line.244"></a>
<span class="sourceLineNo">245</span>    return new CycleDetectingLockFactory(policy);<a name="line.245"></a>
<span class="sourceLineNo">246</span>  }<a name="line.246"></a>
<span class="sourceLineNo">247</span><a name="line.247"></a>
<span class="sourceLineNo">248</span>  /**<a name="line.248"></a>
<span class="sourceLineNo">249</span>   * Equivalent to {@code newReentrantLock(lockName, false)}.<a name="line.249"></a>
<span class="sourceLineNo">250</span>   */<a name="line.250"></a>
<span class="sourceLineNo">251</span>  public ReentrantLock newReentrantLock(String lockName) {<a name="line.251"></a>
<span class="sourceLineNo">252</span>    return newReentrantLock(lockName, false);<a name="line.252"></a>
<span class="sourceLineNo">253</span>  }<a name="line.253"></a>
<span class="sourceLineNo">254</span><a name="line.254"></a>
<span class="sourceLineNo">255</span>  /**<a name="line.255"></a>
<span class="sourceLineNo">256</span>   * Creates a {@link ReentrantLock} with the given fairness policy. The<a name="line.256"></a>
<span class="sourceLineNo">257</span>   * {@code lockName} is used in the warning or exception output to help<a name="line.257"></a>
<span class="sourceLineNo">258</span>   * identify the locks involved in the detected deadlock.<a name="line.258"></a>
<span class="sourceLineNo">259</span>   */<a name="line.259"></a>
<span class="sourceLineNo">260</span>  public ReentrantLock newReentrantLock(String lockName, boolean fair) {<a name="line.260"></a>
<span class="sourceLineNo">261</span>    return policy == Policies.DISABLED ? new ReentrantLock(fair)<a name="line.261"></a>
<span class="sourceLineNo">262</span>        : new CycleDetectingReentrantLock(<a name="line.262"></a>
<span class="sourceLineNo">263</span>            new LockGraphNode(lockName), fair);<a name="line.263"></a>
<span class="sourceLineNo">264</span>  }<a name="line.264"></a>
<span class="sourceLineNo">265</span><a name="line.265"></a>
<span class="sourceLineNo">266</span>  /**<a name="line.266"></a>
<span class="sourceLineNo">267</span>   * Equivalent to {@code newReentrantReadWriteLock(lockName, false)}.<a name="line.267"></a>
<span class="sourceLineNo">268</span>   */<a name="line.268"></a>
<span class="sourceLineNo">269</span>  public ReentrantReadWriteLock newReentrantReadWriteLock(String lockName) {<a name="line.269"></a>
<span class="sourceLineNo">270</span>    return newReentrantReadWriteLock(lockName, false);<a name="line.270"></a>
<span class="sourceLineNo">271</span>  }<a name="line.271"></a>
<span class="sourceLineNo">272</span><a name="line.272"></a>
<span class="sourceLineNo">273</span>  /**<a name="line.273"></a>
<span class="sourceLineNo">274</span>   * Creates a {@link ReentrantReadWriteLock} with the given fairness policy.<a name="line.274"></a>
<span class="sourceLineNo">275</span>   * The {@code lockName} is used in the warning or exception output to help<a name="line.275"></a>
<span class="sourceLineNo">276</span>   * identify the locks involved in the detected deadlock.<a name="line.276"></a>
<span class="sourceLineNo">277</span>   */<a name="line.277"></a>
<span class="sourceLineNo">278</span>  public ReentrantReadWriteLock newReentrantReadWriteLock(<a name="line.278"></a>
<span class="sourceLineNo">279</span>      String lockName, boolean fair) {<a name="line.279"></a>
<span class="sourceLineNo">280</span>    return policy == Policies.DISABLED ? new ReentrantReadWriteLock(fair)<a name="line.280"></a>
<span class="sourceLineNo">281</span>        : new CycleDetectingReentrantReadWriteLock(<a name="line.281"></a>
<span class="sourceLineNo">282</span>            new LockGraphNode(lockName), fair);<a name="line.282"></a>
<span class="sourceLineNo">283</span>  }<a name="line.283"></a>
<span class="sourceLineNo">284</span><a name="line.284"></a>
<span class="sourceLineNo">285</span>  // A static mapping from an Enum type to its set of LockGraphNodes.<a name="line.285"></a>
<span class="sourceLineNo">286</span>  private static final Map&lt;Class&lt;? extends Enum&gt;,<a name="line.286"></a>
<span class="sourceLineNo">287</span>      Map&lt;? extends Enum, LockGraphNode&gt;&gt; lockGraphNodesPerType =<a name="line.287"></a>
<span class="sourceLineNo">288</span>          new MapMaker().weakKeys().makeComputingMap(<a name="line.288"></a>
<span class="sourceLineNo">289</span>              new OrderedLockGraphNodesCreator());<a name="line.289"></a>
<span class="sourceLineNo">290</span><a name="line.290"></a>
<span class="sourceLineNo">291</span>  /**<a name="line.291"></a>
<span class="sourceLineNo">292</span>   * Creates a {@code CycleDetectingLockFactory.WithExplicitOrdering&lt;E&gt;}.<a name="line.292"></a>
<span class="sourceLineNo">293</span>   */<a name="line.293"></a>
<span class="sourceLineNo">294</span>  public static &lt;E extends Enum&lt;E&gt;&gt; WithExplicitOrdering&lt;E&gt;<a name="line.294"></a>
<span class="sourceLineNo">295</span>      newInstanceWithExplicitOrdering(Class&lt;E&gt; enumClass, Policy policy) {<a name="line.295"></a>
<span class="sourceLineNo">296</span>    // OrderedLockGraphNodesCreator maps each enumClass to a Map with the<a name="line.296"></a>
<span class="sourceLineNo">297</span>    // corresponding enum key type.<a name="line.297"></a>
<span class="sourceLineNo">298</span>    checkNotNull(enumClass);<a name="line.298"></a>
<span class="sourceLineNo">299</span>    checkNotNull(policy);<a name="line.299"></a>
<span class="sourceLineNo">300</span>    @SuppressWarnings("unchecked")<a name="line.300"></a>
<span class="sourceLineNo">301</span>    Map&lt;E, LockGraphNode&gt; lockGraphNodes =<a name="line.301"></a>
<span class="sourceLineNo">302</span>        (Map&lt;E, LockGraphNode&gt;) lockGraphNodesPerType.get(enumClass);<a name="line.302"></a>
<span class="sourceLineNo">303</span>    return new WithExplicitOrdering&lt;E&gt;(policy, lockGraphNodes);<a name="line.303"></a>
<span class="sourceLineNo">304</span>  }<a name="line.304"></a>
<span class="sourceLineNo">305</span><a name="line.305"></a>
<span class="sourceLineNo">306</span>  /**<a name="line.306"></a>
<span class="sourceLineNo">307</span>   * A {@code CycleDetectingLockFactory.WithExplicitOrdering} provides the<a name="line.307"></a>
<span class="sourceLineNo">308</span>   * additional enforcement of an application-specified ordering of lock<a name="line.308"></a>
<span class="sourceLineNo">309</span>   * acquisitions. The application defines the allowed ordering with an<a name="line.309"></a>
<span class="sourceLineNo">310</span>   * {@code Enum} whose values each correspond to a lock type. The order in<a name="line.310"></a>
<span class="sourceLineNo">311</span>   * which the values are declared dictates the allowed order of lock<a name="line.311"></a>
<span class="sourceLineNo">312</span>   * acquisition. In other words, locks corresponding to smaller values of<a name="line.312"></a>
<span class="sourceLineNo">313</span>   * {@link Enum#ordinal()} should only be acquired before locks with larger<a name="line.313"></a>
<span class="sourceLineNo">314</span>   * ordinals. Example:<a name="line.314"></a>
<span class="sourceLineNo">315</span>   *<a name="line.315"></a>
<span class="sourceLineNo">316</span>   * &lt;pre&gt;   {@code<a name="line.316"></a>
<span class="sourceLineNo">317</span>   * enum MyLockOrder {<a name="line.317"></a>
<span class="sourceLineNo">318</span>   *   FIRST, SECOND, THIRD;<a name="line.318"></a>
<span class="sourceLineNo">319</span>   * }<a name="line.319"></a>
<span class="sourceLineNo">320</span>   *<a name="line.320"></a>
<span class="sourceLineNo">321</span>   * CycleDetectingLockFactory.WithExplicitOrdering&lt;MyLockOrder&gt; factory =<a name="line.321"></a>
<span class="sourceLineNo">322</span>   *   CycleDetectingLockFactory.newInstanceWithExplicitOrdering(Policies.THROW);<a name="line.322"></a>
<span class="sourceLineNo">323</span>   *<a name="line.323"></a>
<span class="sourceLineNo">324</span>   * Lock lock1 = factory.newReentrantLock(MyLockOrder.FIRST);<a name="line.324"></a>
<span class="sourceLineNo">325</span>   * Lock lock2 = factory.newReentrantLock(MyLockOrder.SECOND);<a name="line.325"></a>
<span class="sourceLineNo">326</span>   * Lock lock3 = factory.newReentrantLock(MyLockOrder.THIRD);<a name="line.326"></a>
<span class="sourceLineNo">327</span>   *<a name="line.327"></a>
<span class="sourceLineNo">328</span>   * lock1.lock();<a name="line.328"></a>
<span class="sourceLineNo">329</span>   * lock3.lock();<a name="line.329"></a>
<span class="sourceLineNo">330</span>   * lock2.lock();  // will throw an IllegalStateException<a name="line.330"></a>
<span class="sourceLineNo">331</span>   * }&lt;/pre&gt;<a name="line.331"></a>
<span class="sourceLineNo">332</span>   *<a name="line.332"></a>
<span class="sourceLineNo">333</span>   * As with all locks created by instances of {@code CycleDetectingLockFactory}<a name="line.333"></a>
<span class="sourceLineNo">334</span>   * explicitly ordered locks participate in general cycle detection with all<a name="line.334"></a>
<span class="sourceLineNo">335</span>   * other cycle detecting locks, and a lock's behavior when detecting a cyclic<a name="line.335"></a>
<span class="sourceLineNo">336</span>   * lock acquisition is defined by the {@code Policy} of the factory that<a name="line.336"></a>
<span class="sourceLineNo">337</span>   * created it.<a name="line.337"></a>
<span class="sourceLineNo">338</span>   * &lt;p&gt;<a name="line.338"></a>
<span class="sourceLineNo">339</span>   * Note, however, that although multiple locks can be created for a given Enum<a name="line.339"></a>
<span class="sourceLineNo">340</span>   * value, whether it be through separate factory instances or through multiple<a name="line.340"></a>
<span class="sourceLineNo">341</span>   * calls to the same factory, attempting to acquire multiple locks with the<a name="line.341"></a>
<span class="sourceLineNo">342</span>   * same Enum value (within the same thread) will result in an<a name="line.342"></a>
<span class="sourceLineNo">343</span>   * IllegalStateException regardless of the factory's policy. For example:<a name="line.343"></a>
<span class="sourceLineNo">344</span>   *<a name="line.344"></a>
<span class="sourceLineNo">345</span>   * &lt;pre&gt;   {@code<a name="line.345"></a>
<span class="sourceLineNo">346</span>   * CycleDetectingLockFactory.WithExplicitOrdering&lt;MyLockOrder&gt; factory1 =<a name="line.346"></a>
<span class="sourceLineNo">347</span>   *   CycleDetectingLockFactory.newInstanceWithExplicitOrdering(...);<a name="line.347"></a>
<span class="sourceLineNo">348</span>   * CycleDetectingLockFactory.WithExplicitOrdering&lt;MyLockOrder&gt; factory2 =<a name="line.348"></a>
<span class="sourceLineNo">349</span>   *   CycleDetectingLockFactory.newInstanceWithExplicitOrdering(...);<a name="line.349"></a>
<span class="sourceLineNo">350</span>   *<a name="line.350"></a>
<span class="sourceLineNo">351</span>   * Lock lockA = factory1.newReentrantLock(MyLockOrder.FIRST);<a name="line.351"></a>
<span class="sourceLineNo">352</span>   * Lock lockB = factory1.newReentrantLock(MyLockOrder.FIRST);<a name="line.352"></a>
<span class="sourceLineNo">353</span>   * Lock lockC = factory2.newReentrantLock(MyLockOrder.FIRST);<a name="line.353"></a>
<span class="sourceLineNo">354</span>   *<a name="line.354"></a>
<span class="sourceLineNo">355</span>   * lockA.lock();<a name="line.355"></a>
<span class="sourceLineNo">356</span>   *<a name="line.356"></a>
<span class="sourceLineNo">357</span>   * lockB.lock();  // will throw an IllegalStateException<a name="line.357"></a>
<span class="sourceLineNo">358</span>   * lockC.lock();  // will throw an IllegalStateException<a name="line.358"></a>
<span class="sourceLineNo">359</span>   *<a name="line.359"></a>
<span class="sourceLineNo">360</span>   * lockA.lock();  // reentrant acquisition is okay<a name="line.360"></a>
<span class="sourceLineNo">361</span>   * }&lt;/pre&gt;<a name="line.361"></a>
<span class="sourceLineNo">362</span>   *<a name="line.362"></a>
<span class="sourceLineNo">363</span>   * It is the responsibility of the application to ensure that multiple lock<a name="line.363"></a>
<span class="sourceLineNo">364</span>   * instances with the same rank are never acquired in the same thread.<a name="line.364"></a>
<span class="sourceLineNo">365</span>   *<a name="line.365"></a>
<span class="sourceLineNo">366</span>   * @param &lt;E&gt; The Enum type representing the explicit lock ordering.<a name="line.366"></a>
<span class="sourceLineNo">367</span>   * @since 13.0<a name="line.367"></a>
<span class="sourceLineNo">368</span>   */<a name="line.368"></a>
<span class="sourceLineNo">369</span>  @Beta<a name="line.369"></a>
<span class="sourceLineNo">370</span>  public static final class WithExplicitOrdering&lt;E extends Enum&lt;E&gt;&gt;<a name="line.370"></a>
<span class="sourceLineNo">371</span>      extends CycleDetectingLockFactory {<a name="line.371"></a>
<span class="sourceLineNo">372</span><a name="line.372"></a>
<span class="sourceLineNo">373</span>    private final Map&lt;E, LockGraphNode&gt; lockGraphNodes;<a name="line.373"></a>
<span class="sourceLineNo">374</span><a name="line.374"></a>
<span class="sourceLineNo">375</span>    @VisibleForTesting<a name="line.375"></a>
<span class="sourceLineNo">376</span>    WithExplicitOrdering(<a name="line.376"></a>
<span class="sourceLineNo">377</span>        Policy policy, Map&lt;E, LockGraphNode&gt; lockGraphNodes) {<a name="line.377"></a>
<span class="sourceLineNo">378</span>      super(policy);<a name="line.378"></a>
<span class="sourceLineNo">379</span>      this.lockGraphNodes = lockGraphNodes;<a name="line.379"></a>
<span class="sourceLineNo">380</span>    }<a name="line.380"></a>
<span class="sourceLineNo">381</span><a name="line.381"></a>
<span class="sourceLineNo">382</span>    /**<a name="line.382"></a>
<span class="sourceLineNo">383</span>     * Equivalent to {@code newReentrantLock(rank, false)}.<a name="line.383"></a>
<span class="sourceLineNo">384</span>     */<a name="line.384"></a>
<span class="sourceLineNo">385</span>    public ReentrantLock newReentrantLock(E rank) {<a name="line.385"></a>
<span class="sourceLineNo">386</span>      return newReentrantLock(rank, false);<a name="line.386"></a>
<span class="sourceLineNo">387</span>    }<a name="line.387"></a>
<span class="sourceLineNo">388</span><a name="line.388"></a>
<span class="sourceLineNo">389</span>    /**<a name="line.389"></a>
<span class="sourceLineNo">390</span>     * Creates a {@link ReentrantLock} with the given fairness policy and rank.<a name="line.390"></a>
<span class="sourceLineNo">391</span>     * The values returned by {@link Enum#getDeclaringClass()} and<a name="line.391"></a>
<span class="sourceLineNo">392</span>     * {@link Enum#name()} are used to describe the lock in warning or<a name="line.392"></a>
<span class="sourceLineNo">393</span>     * exception output.<a name="line.393"></a>
<span class="sourceLineNo">394</span>     *<a name="line.394"></a>
<span class="sourceLineNo">395</span>     * @throws IllegalStateException If the factory has already created a<a name="line.395"></a>
<span class="sourceLineNo">396</span>     *    {@code Lock} with the specified rank.<a name="line.396"></a>
<span class="sourceLineNo">397</span>     */<a name="line.397"></a>
<span class="sourceLineNo">398</span>    public ReentrantLock newReentrantLock(E rank, boolean fair) {<a name="line.398"></a>
<span class="sourceLineNo">399</span>      return policy == Policies.DISABLED ? new ReentrantLock(fair)<a name="line.399"></a>
<span class="sourceLineNo">400</span>          : new CycleDetectingReentrantLock(lockGraphNodes.get(rank), fair);<a name="line.400"></a>
<span class="sourceLineNo">401</span>    }<a name="line.401"></a>
<span class="sourceLineNo">402</span><a name="line.402"></a>
<span class="sourceLineNo">403</span>    /**<a name="line.403"></a>
<span class="sourceLineNo">404</span>     * Equivalent to {@code newReentrantReadWriteLock(rank, false)}.<a name="line.404"></a>
<span class="sourceLineNo">405</span>     */<a name="line.405"></a>
<span class="sourceLineNo">406</span>    public ReentrantReadWriteLock newReentrantReadWriteLock(E rank) {<a name="line.406"></a>
<span class="sourceLineNo">407</span>      return newReentrantReadWriteLock(rank, false);<a name="line.407"></a>
<span class="sourceLineNo">408</span>    }<a name="line.408"></a>
<span class="sourceLineNo">409</span><a name="line.409"></a>
<span class="sourceLineNo">410</span>    /**<a name="line.410"></a>
<span class="sourceLineNo">411</span>     * Creates a {@link ReentrantReadWriteLock} with the given fairness policy<a name="line.411"></a>
<span class="sourceLineNo">412</span>     * and rank. The values returned by {@link Enum#getDeclaringClass()} and<a name="line.412"></a>
<span class="sourceLineNo">413</span>     * {@link Enum#name()} are used to describe the lock in warning or exception<a name="line.413"></a>
<span class="sourceLineNo">414</span>     * output.<a name="line.414"></a>
<span class="sourceLineNo">415</span>     *<a name="line.415"></a>
<span class="sourceLineNo">416</span>     * @throws IllegalStateException If the factory has already created a<a name="line.416"></a>
<span class="sourceLineNo">417</span>     *    {@code Lock} with the specified rank.<a name="line.417"></a>
<span class="sourceLineNo">418</span>     */<a name="line.418"></a>
<span class="sourceLineNo">419</span>    public ReentrantReadWriteLock newReentrantReadWriteLock(<a name="line.419"></a>
<span class="sourceLineNo">420</span>        E rank, boolean fair) {<a name="line.420"></a>
<span class="sourceLineNo">421</span>      return policy == Policies.DISABLED ? new ReentrantReadWriteLock(fair)<a name="line.421"></a>
<span class="sourceLineNo">422</span>          : new CycleDetectingReentrantReadWriteLock(<a name="line.422"></a>
<span class="sourceLineNo">423</span>              lockGraphNodes.get(rank), fair);<a name="line.423"></a>
<span class="sourceLineNo">424</span>    }<a name="line.424"></a>
<span class="sourceLineNo">425</span>  }<a name="line.425"></a>
<span class="sourceLineNo">426</span><a name="line.426"></a>
<span class="sourceLineNo">427</span>  /**<a name="line.427"></a>
<span class="sourceLineNo">428</span>   * For a given Enum type, creates an immutable map from each of the Enum's<a name="line.428"></a>
<span class="sourceLineNo">429</span>   * values to a corresponding LockGraphNode, with the<a name="line.429"></a>
<span class="sourceLineNo">430</span>   * {@code allowedPriorLocks} and {@code disallowedPriorLocks} prepopulated<a name="line.430"></a>
<span class="sourceLineNo">431</span>   * with nodes according to the natural ordering of the associated Enum values.<a name="line.431"></a>
<span class="sourceLineNo">432</span>   */<a name="line.432"></a>
<span class="sourceLineNo">433</span>  @VisibleForTesting<a name="line.433"></a>
<span class="sourceLineNo">434</span>  static class OrderedLockGraphNodesCreator<a name="line.434"></a>
<span class="sourceLineNo">435</span>      implements Function&lt;Class&lt;? extends Enum&gt;,<a name="line.435"></a>
<span class="sourceLineNo">436</span>          Map&lt;? extends Enum, LockGraphNode&gt;&gt; {<a name="line.436"></a>
<span class="sourceLineNo">437</span><a name="line.437"></a>
<span class="sourceLineNo">438</span>    @Override<a name="line.438"></a>
<span class="sourceLineNo">439</span>    @SuppressWarnings("unchecked")  // There's no way to properly express with<a name="line.439"></a>
<span class="sourceLineNo">440</span>    // wildcards the recursive Enum type required by createNodesFor(), and the<a name="line.440"></a>
<span class="sourceLineNo">441</span>    // Map/Function types must use wildcards since they accept any Enum class.<a name="line.441"></a>
<span class="sourceLineNo">442</span>    public Map&lt;? extends Enum, LockGraphNode&gt; apply(<a name="line.442"></a>
<span class="sourceLineNo">443</span>        Class&lt;? extends Enum&gt; clazz) {<a name="line.443"></a>
<span class="sourceLineNo">444</span>      return createNodesFor(clazz);<a name="line.444"></a>
<span class="sourceLineNo">445</span>    }<a name="line.445"></a>
<span class="sourceLineNo">446</span><a name="line.446"></a>
<span class="sourceLineNo">447</span>    &lt;E extends Enum&lt;E&gt;&gt; Map&lt;E, LockGraphNode&gt; createNodesFor(Class&lt;E&gt; clazz) {<a name="line.447"></a>
<span class="sourceLineNo">448</span>      EnumMap&lt;E, LockGraphNode&gt; map = Maps.newEnumMap(clazz);<a name="line.448"></a>
<span class="sourceLineNo">449</span>      E[] keys = clazz.getEnumConstants();<a name="line.449"></a>
<span class="sourceLineNo">450</span>      final int numKeys = keys.length;<a name="line.450"></a>
<span class="sourceLineNo">451</span>      ArrayList&lt;LockGraphNode&gt; nodes =<a name="line.451"></a>
<span class="sourceLineNo">452</span>          Lists.newArrayListWithCapacity(numKeys);<a name="line.452"></a>
<span class="sourceLineNo">453</span>      // Create a LockGraphNode for each enum value.<a name="line.453"></a>
<span class="sourceLineNo">454</span>      for (E key : keys) {<a name="line.454"></a>
<span class="sourceLineNo">455</span>        LockGraphNode node = new LockGraphNode(getLockName(key));<a name="line.455"></a>
<span class="sourceLineNo">456</span>        nodes.add(node);<a name="line.456"></a>
<span class="sourceLineNo">457</span>        map.put(key, node);<a name="line.457"></a>
<span class="sourceLineNo">458</span>      }<a name="line.458"></a>
<span class="sourceLineNo">459</span>      // Pre-populate all allowedPriorLocks with nodes of smaller ordinal.<a name="line.459"></a>
<span class="sourceLineNo">460</span>      for (int i = 1; i &lt; numKeys; i++) {<a name="line.460"></a>
<span class="sourceLineNo">461</span>        nodes.get(i).checkAcquiredLocks(Policies.THROW, nodes.subList(0, i));<a name="line.461"></a>
<span class="sourceLineNo">462</span>      }<a name="line.462"></a>
<span class="sourceLineNo">463</span>      // Pre-populate all disallowedPriorLocks with nodes of larger ordinal.<a name="line.463"></a>
<span class="sourceLineNo">464</span>      for (int i = 0; i &lt; numKeys - 1; i++) {<a name="line.464"></a>
<span class="sourceLineNo">465</span>        nodes.get(i).checkAcquiredLocks(<a name="line.465"></a>
<span class="sourceLineNo">466</span>            Policies.DISABLED, nodes.subList(i + 1, numKeys));<a name="line.466"></a>
<span class="sourceLineNo">467</span>      }<a name="line.467"></a>
<span class="sourceLineNo">468</span>      return Collections.unmodifiableMap(map);<a name="line.468"></a>
<span class="sourceLineNo">469</span>    }<a name="line.469"></a>
<span class="sourceLineNo">470</span><a name="line.470"></a>
<span class="sourceLineNo">471</span>    /**<a name="line.471"></a>
<span class="sourceLineNo">472</span>     * For the given Enum value {@code rank}, returns the value's<a name="line.472"></a>
<span class="sourceLineNo">473</span>     * {@code "EnumClass.name"}, which is used in exception and warning<a name="line.473"></a>
<span class="sourceLineNo">474</span>     * output.<a name="line.474"></a>
<span class="sourceLineNo">475</span>     */<a name="line.475"></a>
<span class="sourceLineNo">476</span>    private String getLockName(Enum&lt;?&gt; rank) {<a name="line.476"></a>
<span class="sourceLineNo">477</span>      return rank.getDeclaringClass().getSimpleName() + "." + rank.name();<a name="line.477"></a>
<span class="sourceLineNo">478</span>    }<a name="line.478"></a>
<span class="sourceLineNo">479</span>  }<a name="line.479"></a>
<span class="sourceLineNo">480</span><a name="line.480"></a>
<span class="sourceLineNo">481</span>  //////// Implementation /////////<a name="line.481"></a>
<span class="sourceLineNo">482</span><a name="line.482"></a>
<span class="sourceLineNo">483</span>  private static final Logger logger = Logger.getLogger(<a name="line.483"></a>
<span class="sourceLineNo">484</span>      CycleDetectingLockFactory.class.getName());<a name="line.484"></a>
<span class="sourceLineNo">485</span><a name="line.485"></a>
<span class="sourceLineNo">486</span>  final Policy policy;<a name="line.486"></a>
<span class="sourceLineNo">487</span><a name="line.487"></a>
<span class="sourceLineNo">488</span>  private CycleDetectingLockFactory(Policy policy) {<a name="line.488"></a>
<span class="sourceLineNo">489</span>    this.policy = checkNotNull(policy);<a name="line.489"></a>
<span class="sourceLineNo">490</span>  }<a name="line.490"></a>
<span class="sourceLineNo">491</span><a name="line.491"></a>
<span class="sourceLineNo">492</span>  /**<a name="line.492"></a>
<span class="sourceLineNo">493</span>   * Tracks the currently acquired locks for each Thread, kept up to date by<a name="line.493"></a>
<span class="sourceLineNo">494</span>   * calls to {@link #aboutToAcquire(CycleDetectingLock)} and<a name="line.494"></a>
<span class="sourceLineNo">495</span>   * {@link #lockStateChanged(CycleDetectingLock)}.<a name="line.495"></a>
<span class="sourceLineNo">496</span>   */<a name="line.496"></a>
<span class="sourceLineNo">497</span>  // This is logically a Set, but an ArrayList is used to minimize the amount<a name="line.497"></a>
<span class="sourceLineNo">498</span>  // of allocation done on lock()/unlock().<a name="line.498"></a>
<span class="sourceLineNo">499</span>  private static final ThreadLocal&lt;ArrayList&lt;LockGraphNode&gt;&gt;<a name="line.499"></a>
<span class="sourceLineNo">500</span>      acquiredLocks = new ThreadLocal&lt;ArrayList&lt;LockGraphNode&gt;&gt;() {<a name="line.500"></a>
<span class="sourceLineNo">501</span>    @Override<a name="line.501"></a>
<span class="sourceLineNo">502</span>    protected ArrayList&lt;LockGraphNode&gt; initialValue() {<a name="line.502"></a>
<span class="sourceLineNo">503</span>      return Lists.&lt;LockGraphNode&gt;newArrayListWithCapacity(3);<a name="line.503"></a>
<span class="sourceLineNo">504</span>    }<a name="line.504"></a>
<span class="sourceLineNo">505</span>  };<a name="line.505"></a>
<span class="sourceLineNo">506</span><a name="line.506"></a>
<span class="sourceLineNo">507</span>  /**<a name="line.507"></a>
<span class="sourceLineNo">508</span>   * A Throwable used to record a stack trace that illustrates an example of<a name="line.508"></a>
<span class="sourceLineNo">509</span>   * a specific lock acquisition ordering. The top of the stack trace is<a name="line.509"></a>
<span class="sourceLineNo">510</span>   * truncated such that it starts with the acquisition of the lock in<a name="line.510"></a>
<span class="sourceLineNo">511</span>   * question, e.g.<a name="line.511"></a>
<span class="sourceLineNo">512</span>   *<a name="line.512"></a>
<span class="sourceLineNo">513</span>   * &lt;pre&gt;<a name="line.513"></a>
<span class="sourceLineNo">514</span>   * com...ExampleStackTrace: LockB -&amp;gt; LockC<a name="line.514"></a>
<span class="sourceLineNo">515</span>   *   at com...CycleDetectingReentrantLock.lock(CycleDetectingLockFactory.java:443)<a name="line.515"></a>
<span class="sourceLineNo">516</span>   *   at ...<a name="line.516"></a>
<span class="sourceLineNo">517</span>   *   at ...<a name="line.517"></a>
<span class="sourceLineNo">518</span>   *   at com...MyClass.someMethodThatAcquiresLockB(MyClass.java:123)<a name="line.518"></a>
<span class="sourceLineNo">519</span>   * &lt;/pre&gt;<a name="line.519"></a>
<span class="sourceLineNo">520</span>   */<a name="line.520"></a>
<span class="sourceLineNo">521</span>  private static class ExampleStackTrace extends IllegalStateException {<a name="line.521"></a>
<span class="sourceLineNo">522</span><a name="line.522"></a>
<span class="sourceLineNo">523</span>    static final StackTraceElement[] EMPTY_STACK_TRACE =<a name="line.523"></a>
<span class="sourceLineNo">524</span>        new StackTraceElement[0];<a name="line.524"></a>
<span class="sourceLineNo">525</span><a name="line.525"></a>
<span class="sourceLineNo">526</span>    static Set&lt;String&gt; EXCLUDED_CLASS_NAMES = ImmutableSet.of(<a name="line.526"></a>
<span class="sourceLineNo">527</span>        CycleDetectingLockFactory.class.getName(),<a name="line.527"></a>
<span class="sourceLineNo">528</span>        ExampleStackTrace.class.getName(),<a name="line.528"></a>
<span class="sourceLineNo">529</span>        LockGraphNode.class.getName());<a name="line.529"></a>
<span class="sourceLineNo">530</span><a name="line.530"></a>
<span class="sourceLineNo">531</span>    ExampleStackTrace(LockGraphNode node1, LockGraphNode node2) {<a name="line.531"></a>
<span class="sourceLineNo">532</span>      super(node1.getLockName() + " -&gt; " + node2.getLockName());<a name="line.532"></a>
<span class="sourceLineNo">533</span>      StackTraceElement[] origStackTrace = getStackTrace();<a name="line.533"></a>
<span class="sourceLineNo">534</span>      for (int i = 0, n = origStackTrace.length; i &lt; n; i++) {<a name="line.534"></a>
<span class="sourceLineNo">535</span>        if (WithExplicitOrdering.class.getName().equals(<a name="line.535"></a>
<span class="sourceLineNo">536</span>                origStackTrace[i].getClassName())) {<a name="line.536"></a>
<span class="sourceLineNo">537</span>          // For pre-populated disallowedPriorLocks edges, omit the stack trace.<a name="line.537"></a>
<span class="sourceLineNo">538</span>          setStackTrace(EMPTY_STACK_TRACE);<a name="line.538"></a>
<span class="sourceLineNo">539</span>          break;<a name="line.539"></a>
<span class="sourceLineNo">540</span>        }<a name="line.540"></a>
<span class="sourceLineNo">541</span>        if (!EXCLUDED_CLASS_NAMES.contains(origStackTrace[i].getClassName())) {<a name="line.541"></a>
<span class="sourceLineNo">542</span>          setStackTrace(Arrays.copyOfRange(origStackTrace, i, n));<a name="line.542"></a>
<span class="sourceLineNo">543</span>          break;<a name="line.543"></a>
<span class="sourceLineNo">544</span>        }<a name="line.544"></a>
<span class="sourceLineNo">545</span>      }<a name="line.545"></a>
<span class="sourceLineNo">546</span>    }<a name="line.546"></a>
<span class="sourceLineNo">547</span>  }<a name="line.547"></a>
<span class="sourceLineNo">548</span><a name="line.548"></a>
<span class="sourceLineNo">549</span>  /**<a name="line.549"></a>
<span class="sourceLineNo">550</span>   * Represents a detected cycle in lock acquisition ordering. The exception<a name="line.550"></a>
<span class="sourceLineNo">551</span>   * includes a causal chain of {@code ExampleStackTrace} instances to illustrate the<a name="line.551"></a>
<span class="sourceLineNo">552</span>   * cycle, e.g.<a name="line.552"></a>
<span class="sourceLineNo">553</span>   *<a name="line.553"></a>
<span class="sourceLineNo">554</span>   * &lt;pre&gt;<a name="line.554"></a>
<span class="sourceLineNo">555</span>   * com....PotentialDeadlockException: Potential Deadlock from LockC -&amp;gt; ReadWriteA<a name="line.555"></a>
<span class="sourceLineNo">556</span>   *   at ...<a name="line.556"></a>
<span class="sourceLineNo">557</span>   *   at ...<a name="line.557"></a>
<span class="sourceLineNo">558</span>   * Caused by: com...ExampleStackTrace: LockB -&amp;gt; LockC<a name="line.558"></a>
<span class="sourceLineNo">559</span>   *   at ...<a name="line.559"></a>
<span class="sourceLineNo">560</span>   *   at ...<a name="line.560"></a>
<span class="sourceLineNo">561</span>   * Caused by: com...ExampleStackTrace: ReadWriteA -&amp;gt; LockB<a name="line.561"></a>
<span class="sourceLineNo">562</span>   *   at ...<a name="line.562"></a>
<span class="sourceLineNo">563</span>   *   at ...<a name="line.563"></a>
<span class="sourceLineNo">564</span>   * &lt;/pre&gt;<a name="line.564"></a>
<span class="sourceLineNo">565</span>   *<a name="line.565"></a>
<span class="sourceLineNo">566</span>   * Instances are logged for the {@code Policies.WARN}, and thrown for<a name="line.566"></a>
<span class="sourceLineNo">567</span>   * {@code Policies.THROW}.<a name="line.567"></a>
<span class="sourceLineNo">568</span>   *<a name="line.568"></a>
<span class="sourceLineNo">569</span>   * @since 13.0<a name="line.569"></a>
<span class="sourceLineNo">570</span>   */<a name="line.570"></a>
<span class="sourceLineNo">571</span>  @Beta<a name="line.571"></a>
<span class="sourceLineNo">572</span>  public static final class PotentialDeadlockException<a name="line.572"></a>
<span class="sourceLineNo">573</span>      extends ExampleStackTrace {<a name="line.573"></a>
<span class="sourceLineNo">574</span><a name="line.574"></a>
<span class="sourceLineNo">575</span>    private final ExampleStackTrace conflictingStackTrace;<a name="line.575"></a>
<span class="sourceLineNo">576</span><a name="line.576"></a>
<span class="sourceLineNo">577</span>    private PotentialDeadlockException(<a name="line.577"></a>
<span class="sourceLineNo">578</span>        LockGraphNode node1,<a name="line.578"></a>
<span class="sourceLineNo">579</span>        LockGraphNode node2,<a name="line.579"></a>
<span class="sourceLineNo">580</span>        ExampleStackTrace conflictingStackTrace) {<a name="line.580"></a>
<span class="sourceLineNo">581</span>      super(node1, node2);<a name="line.581"></a>
<span class="sourceLineNo">582</span>      this.conflictingStackTrace = conflictingStackTrace;<a name="line.582"></a>
<span class="sourceLineNo">583</span>      initCause(conflictingStackTrace);<a name="line.583"></a>
<span class="sourceLineNo">584</span>    }<a name="line.584"></a>
<span class="sourceLineNo">585</span><a name="line.585"></a>
<span class="sourceLineNo">586</span>    public ExampleStackTrace getConflictingStackTrace() {<a name="line.586"></a>
<span class="sourceLineNo">587</span>      return conflictingStackTrace;<a name="line.587"></a>
<span class="sourceLineNo">588</span>    }<a name="line.588"></a>
<span class="sourceLineNo">589</span><a name="line.589"></a>
<span class="sourceLineNo">590</span>    /**<a name="line.590"></a>
<span class="sourceLineNo">591</span>     * Appends the chain of messages from the {@code conflictingStackTrace} to<a name="line.591"></a>
<span class="sourceLineNo">592</span>     * the original {@code message}.<a name="line.592"></a>
<span class="sourceLineNo">593</span>     */<a name="line.593"></a>
<span class="sourceLineNo">594</span>    @Override<a name="line.594"></a>
<span class="sourceLineNo">595</span>    public String getMessage() {<a name="line.595"></a>
<span class="sourceLineNo">596</span>      StringBuilder message = new StringBuilder(super.getMessage());<a name="line.596"></a>
<span class="sourceLineNo">597</span>      for (Throwable t = conflictingStackTrace; t != null; t = t.getCause()) {<a name="line.597"></a>
<span class="sourceLineNo">598</span>        message.append(", ").append(t.getMessage());<a name="line.598"></a>
<span class="sourceLineNo">599</span>      }<a name="line.599"></a>
<span class="sourceLineNo">600</span>      return message.toString();<a name="line.600"></a>
<span class="sourceLineNo">601</span>    }<a name="line.601"></a>
<span class="sourceLineNo">602</span>  }<a name="line.602"></a>
<span class="sourceLineNo">603</span><a name="line.603"></a>
<span class="sourceLineNo">604</span>  /**<a name="line.604"></a>
<span class="sourceLineNo">605</span>   * Internal Lock implementations implement the {@code CycleDetectingLock}<a name="line.605"></a>
<span class="sourceLineNo">606</span>   * interface, allowing the detection logic to treat all locks in the same<a name="line.606"></a>
<span class="sourceLineNo">607</span>   * manner.<a name="line.607"></a>
<span class="sourceLineNo">608</span>   */<a name="line.608"></a>
<span class="sourceLineNo">609</span>  private interface CycleDetectingLock {<a name="line.609"></a>
<span class="sourceLineNo">610</span><a name="line.610"></a>
<span class="sourceLineNo">611</span>    /** @return the {@link LockGraphNode} associated with this lock. */<a name="line.611"></a>
<span class="sourceLineNo">612</span>    LockGraphNode getLockGraphNode();<a name="line.612"></a>
<span class="sourceLineNo">613</span><a name="line.613"></a>
<span class="sourceLineNo">614</span>    /** @return {@code true} if the current thread has acquired this lock. */<a name="line.614"></a>
<span class="sourceLineNo">615</span>    boolean isAcquiredByCurrentThread();<a name="line.615"></a>
<span class="sourceLineNo">616</span>  }<a name="line.616"></a>
<span class="sourceLineNo">617</span><a name="line.617"></a>
<span class="sourceLineNo">618</span>  /**<a name="line.618"></a>
<span class="sourceLineNo">619</span>   * A {@code LockGraphNode} associated with each lock instance keeps track of<a name="line.619"></a>
<span class="sourceLineNo">620</span>   * the directed edges in the lock acquisition graph.<a name="line.620"></a>
<span class="sourceLineNo">621</span>   */<a name="line.621"></a>
<span class="sourceLineNo">622</span>  private static class LockGraphNode {<a name="line.622"></a>
<span class="sourceLineNo">623</span><a name="line.623"></a>
<span class="sourceLineNo">624</span>    /**<a name="line.624"></a>
<span class="sourceLineNo">625</span>     * The map tracking the locks that are known to be acquired before this<a name="line.625"></a>
<span class="sourceLineNo">626</span>     * lock, each associated with an example stack trace. Locks are weakly keyed<a name="line.626"></a>
<span class="sourceLineNo">627</span>     * to allow proper garbage collection when they are no longer referenced.<a name="line.627"></a>
<span class="sourceLineNo">628</span>     */<a name="line.628"></a>
<span class="sourceLineNo">629</span>    final Map&lt;LockGraphNode, ExampleStackTrace&gt; allowedPriorLocks =<a name="line.629"></a>
<span class="sourceLineNo">630</span>        new MapMaker().weakKeys().makeMap();<a name="line.630"></a>
<span class="sourceLineNo">631</span><a name="line.631"></a>
<span class="sourceLineNo">632</span>    /**<a name="line.632"></a>
<span class="sourceLineNo">633</span>     * The map tracking lock nodes that can cause a lock acquisition cycle if<a name="line.633"></a>
<span class="sourceLineNo">634</span>     * acquired before this node.<a name="line.634"></a>
<span class="sourceLineNo">635</span>     */<a name="line.635"></a>
<span class="sourceLineNo">636</span>    final Map&lt;LockGraphNode, PotentialDeadlockException&gt;<a name="line.636"></a>
<span class="sourceLineNo">637</span>        disallowedPriorLocks = new MapMaker().weakKeys().makeMap();<a name="line.637"></a>
<span class="sourceLineNo">638</span><a name="line.638"></a>
<span class="sourceLineNo">639</span>    final String lockName;<a name="line.639"></a>
<span class="sourceLineNo">640</span><a name="line.640"></a>
<span class="sourceLineNo">641</span>    LockGraphNode(String lockName) {<a name="line.641"></a>
<span class="sourceLineNo">642</span>      this.lockName = Preconditions.checkNotNull(lockName);<a name="line.642"></a>
<span class="sourceLineNo">643</span>    }<a name="line.643"></a>
<span class="sourceLineNo">644</span><a name="line.644"></a>
<span class="sourceLineNo">645</span>    String getLockName() {<a name="line.645"></a>
<span class="sourceLineNo">646</span>      return lockName;<a name="line.646"></a>
<span class="sourceLineNo">647</span>    }<a name="line.647"></a>
<span class="sourceLineNo">648</span><a name="line.648"></a>
<span class="sourceLineNo">649</span>    void checkAcquiredLocks(<a name="line.649"></a>
<span class="sourceLineNo">650</span>        Policy policy, List&lt;LockGraphNode&gt; acquiredLocks) {<a name="line.650"></a>
<span class="sourceLineNo">651</span>      for (int i = 0, size = acquiredLocks.size(); i &lt; size; i++) {<a name="line.651"></a>
<span class="sourceLineNo">652</span>        checkAcquiredLock(policy, acquiredLocks.get(i));<a name="line.652"></a>
<span class="sourceLineNo">653</span>      }<a name="line.653"></a>
<span class="sourceLineNo">654</span>    }<a name="line.654"></a>
<span class="sourceLineNo">655</span><a name="line.655"></a>
<span class="sourceLineNo">656</span>    /**<a name="line.656"></a>
<span class="sourceLineNo">657</span>     * Checks the acquisition-ordering between {@code this}, which is about to<a name="line.657"></a>
<span class="sourceLineNo">658</span>     * be acquired, and the specified {@code acquiredLock}.<a name="line.658"></a>
<span class="sourceLineNo">659</span>     * &lt;p&gt;<a name="line.659"></a>
<span class="sourceLineNo">660</span>     * When this method returns, the {@code acquiredLock} should be in either<a name="line.660"></a>
<span class="sourceLineNo">661</span>     * the {@code preAcquireLocks} map, for the case in which it is safe to<a name="line.661"></a>
<span class="sourceLineNo">662</span>     * acquire {@code this} after the {@code acquiredLock}, or in the<a name="line.662"></a>
<span class="sourceLineNo">663</span>     * {@code disallowedPriorLocks} map, in which case it is not safe.<a name="line.663"></a>
<span class="sourceLineNo">664</span>     */<a name="line.664"></a>
<span class="sourceLineNo">665</span>    void checkAcquiredLock(Policy policy, LockGraphNode acquiredLock) {<a name="line.665"></a>
<span class="sourceLineNo">666</span>      // checkAcquiredLock() should never be invoked by a lock that has already<a name="line.666"></a>
<span class="sourceLineNo">667</span>      // been acquired. For unordered locks, aboutToAcquire() ensures this by<a name="line.667"></a>
<span class="sourceLineNo">668</span>      // checking isAcquiredByCurrentThread(). For ordered locks, however, this<a name="line.668"></a>
<span class="sourceLineNo">669</span>      // can happen because multiple locks may share the same LockGraphNode. In<a name="line.669"></a>
<span class="sourceLineNo">670</span>      // this situation, throw an IllegalStateException as defined by contract<a name="line.670"></a>
<span class="sourceLineNo">671</span>      // described in the documentation of WithExplicitOrdering.<a name="line.671"></a>
<span class="sourceLineNo">672</span>      Preconditions.checkState(<a name="line.672"></a>
<span class="sourceLineNo">673</span>          this != acquiredLock,<a name="line.673"></a>
<span class="sourceLineNo">674</span>          "Attempted to acquire multiple locks with the same rank " +<a name="line.674"></a>
<span class="sourceLineNo">675</span>          acquiredLock.getLockName());<a name="line.675"></a>
<span class="sourceLineNo">676</span><a name="line.676"></a>
<span class="sourceLineNo">677</span>      if (allowedPriorLocks.containsKey(acquiredLock)) {<a name="line.677"></a>
<span class="sourceLineNo">678</span>        // The acquisition ordering from "acquiredLock" to "this" has already<a name="line.678"></a>
<span class="sourceLineNo">679</span>        // been verified as safe. In a properly written application, this is<a name="line.679"></a>
<span class="sourceLineNo">680</span>        // the common case.<a name="line.680"></a>
<span class="sourceLineNo">681</span>        return;<a name="line.681"></a>
<span class="sourceLineNo">682</span>      }<a name="line.682"></a>
<span class="sourceLineNo">683</span>      PotentialDeadlockException previousDeadlockException =<a name="line.683"></a>
<span class="sourceLineNo">684</span>          disallowedPriorLocks.get(acquiredLock);<a name="line.684"></a>
<span class="sourceLineNo">685</span>      if (previousDeadlockException != null) {<a name="line.685"></a>
<span class="sourceLineNo">686</span>        // Previously determined to be an unsafe lock acquisition.<a name="line.686"></a>
<span class="sourceLineNo">687</span>        // Create a new PotentialDeadlockException with the same causal chain<a name="line.687"></a>
<span class="sourceLineNo">688</span>        // (the example cycle) as that of the cached exception.<a name="line.688"></a>
<span class="sourceLineNo">689</span>        PotentialDeadlockException exception = new PotentialDeadlockException(<a name="line.689"></a>
<span class="sourceLineNo">690</span>            acquiredLock, this,<a name="line.690"></a>
<span class="sourceLineNo">691</span>            previousDeadlockException.getConflictingStackTrace());<a name="line.691"></a>
<span class="sourceLineNo">692</span>        policy.handlePotentialDeadlock(exception);<a name="line.692"></a>
<span class="sourceLineNo">693</span>        return;<a name="line.693"></a>
<span class="sourceLineNo">694</span>      }<a name="line.694"></a>
<span class="sourceLineNo">695</span>      // Otherwise, it's the first time seeing this lock relationship. Look for<a name="line.695"></a>
<span class="sourceLineNo">696</span>      // a path from the acquiredLock to this.<a name="line.696"></a>
<span class="sourceLineNo">697</span>      Set&lt;LockGraphNode&gt; seen = Sets.newIdentityHashSet();<a name="line.697"></a>
<span class="sourceLineNo">698</span>      ExampleStackTrace path = acquiredLock.findPathTo(this, seen);<a name="line.698"></a>
<span class="sourceLineNo">699</span><a name="line.699"></a>
<span class="sourceLineNo">700</span>      if (path == null) {<a name="line.700"></a>
<span class="sourceLineNo">701</span>        // this can be safely acquired after the acquiredLock.<a name="line.701"></a>
<span class="sourceLineNo">702</span>        //<a name="line.702"></a>
<span class="sourceLineNo">703</span>        // Note that there is a race condition here which can result in missing<a name="line.703"></a>
<span class="sourceLineNo">704</span>        // a cyclic edge: it's possible for two threads to simultaneous find<a name="line.704"></a>
<span class="sourceLineNo">705</span>        // "safe" edges which together form a cycle. Preventing this race<a name="line.705"></a>
<span class="sourceLineNo">706</span>        // condition efficiently without _introducing_ deadlock is probably<a name="line.706"></a>
<span class="sourceLineNo">707</span>        // tricky. For now, just accept the race condition---missing a warning<a name="line.707"></a>
<span class="sourceLineNo">708</span>        // now and then is still better than having no deadlock detection.<a name="line.708"></a>
<span class="sourceLineNo">709</span>        allowedPriorLocks.put(<a name="line.709"></a>
<span class="sourceLineNo">710</span>            acquiredLock, new ExampleStackTrace(acquiredLock, this));<a name="line.710"></a>
<span class="sourceLineNo">711</span>      } else {<a name="line.711"></a>
<span class="sourceLineNo">712</span>        // Unsafe acquisition order detected. Create and cache a<a name="line.712"></a>
<span class="sourceLineNo">713</span>        // PotentialDeadlockException.<a name="line.713"></a>
<span class="sourceLineNo">714</span>        PotentialDeadlockException exception =<a name="line.714"></a>
<span class="sourceLineNo">715</span>            new PotentialDeadlockException(acquiredLock, this, path);<a name="line.715"></a>
<span class="sourceLineNo">716</span>        disallowedPriorLocks.put(acquiredLock, exception);<a name="line.716"></a>
<span class="sourceLineNo">717</span>        policy.handlePotentialDeadlock(exception);<a name="line.717"></a>
<span class="sourceLineNo">718</span>      }<a name="line.718"></a>
<span class="sourceLineNo">719</span>    }<a name="line.719"></a>
<span class="sourceLineNo">720</span><a name="line.720"></a>
<span class="sourceLineNo">721</span>    /**<a name="line.721"></a>
<span class="sourceLineNo">722</span>     * Performs a depth-first traversal of the graph edges defined by each<a name="line.722"></a>
<span class="sourceLineNo">723</span>     * node's {@code allowedPriorLocks} to find a path between {@code this} and<a name="line.723"></a>
<span class="sourceLineNo">724</span>     * the specified {@code lock}.<a name="line.724"></a>
<span class="sourceLineNo">725</span>     *<a name="line.725"></a>
<span class="sourceLineNo">726</span>     * @return If a path was found, a chained {@link ExampleStackTrace}<a name="line.726"></a>
<span class="sourceLineNo">727</span>     *     illustrating the path to the {@code lock}, or {@code null} if no path<a name="line.727"></a>
<span class="sourceLineNo">728</span>     *     was found.<a name="line.728"></a>
<span class="sourceLineNo">729</span>     */<a name="line.729"></a>
<span class="sourceLineNo">730</span>    @Nullable<a name="line.730"></a>
<span class="sourceLineNo">731</span>    private ExampleStackTrace findPathTo(<a name="line.731"></a>
<span class="sourceLineNo">732</span>        LockGraphNode node, Set&lt;LockGraphNode&gt; seen) {<a name="line.732"></a>
<span class="sourceLineNo">733</span>      if (!seen.add(this)) {<a name="line.733"></a>
<span class="sourceLineNo">734</span>        return null;  // Already traversed this node.<a name="line.734"></a>
<span class="sourceLineNo">735</span>      }<a name="line.735"></a>
<span class="sourceLineNo">736</span>      ExampleStackTrace found = allowedPriorLocks.get(node);<a name="line.736"></a>
<span class="sourceLineNo">737</span>      if (found != null) {<a name="line.737"></a>
<span class="sourceLineNo">738</span>        return found;  // Found a path ending at the node!<a name="line.738"></a>
<span class="sourceLineNo">739</span>      }<a name="line.739"></a>
<span class="sourceLineNo">740</span>      // Recurse the edges.<a name="line.740"></a>
<span class="sourceLineNo">741</span>      for (Map.Entry&lt;LockGraphNode, ExampleStackTrace&gt; entry :<a name="line.741"></a>
<span class="sourceLineNo">742</span>               allowedPriorLocks.entrySet()) {<a name="line.742"></a>
<span class="sourceLineNo">743</span>        LockGraphNode preAcquiredLock = entry.getKey();<a name="line.743"></a>
<span class="sourceLineNo">744</span>        found = preAcquiredLock.findPathTo(node, seen);<a name="line.744"></a>
<span class="sourceLineNo">745</span>        if (found != null) {<a name="line.745"></a>
<span class="sourceLineNo">746</span>          // One of this node's allowedPriorLocks found a path. Prepend an<a name="line.746"></a>
<span class="sourceLineNo">747</span>          // ExampleStackTrace(preAcquiredLock, this) to the returned chain of<a name="line.747"></a>
<span class="sourceLineNo">748</span>          // ExampleStackTraces.<a name="line.748"></a>
<span class="sourceLineNo">749</span>          ExampleStackTrace path =<a name="line.749"></a>
<span class="sourceLineNo">750</span>              new ExampleStackTrace(preAcquiredLock, this);<a name="line.750"></a>
<span class="sourceLineNo">751</span>          path.setStackTrace(entry.getValue().getStackTrace());<a name="line.751"></a>
<span class="sourceLineNo">752</span>          path.initCause(found);<a name="line.752"></a>
<span class="sourceLineNo">753</span>          return path;<a name="line.753"></a>
<span class="sourceLineNo">754</span>        }<a name="line.754"></a>
<span class="sourceLineNo">755</span>      }<a name="line.755"></a>
<span class="sourceLineNo">756</span>      return null;<a name="line.756"></a>
<span class="sourceLineNo">757</span>    }<a name="line.757"></a>
<span class="sourceLineNo">758</span>  }<a name="line.758"></a>
<span class="sourceLineNo">759</span><a name="line.759"></a>
<span class="sourceLineNo">760</span>  /**<a name="line.760"></a>
<span class="sourceLineNo">761</span>   * CycleDetectingLock implementations must call this method before attempting<a name="line.761"></a>
<span class="sourceLineNo">762</span>   * to acquire the lock.<a name="line.762"></a>
<span class="sourceLineNo">763</span>   */<a name="line.763"></a>
<span class="sourceLineNo">764</span>  private void aboutToAcquire(CycleDetectingLock lock) {<a name="line.764"></a>
<span class="sourceLineNo">765</span>    if (!lock.isAcquiredByCurrentThread()) {<a name="line.765"></a>
<span class="sourceLineNo">766</span>      ArrayList&lt;LockGraphNode&gt; acquiredLockList = acquiredLocks.get();<a name="line.766"></a>
<span class="sourceLineNo">767</span>      LockGraphNode node = lock.getLockGraphNode();<a name="line.767"></a>
<span class="sourceLineNo">768</span>      node.checkAcquiredLocks(policy, acquiredLockList);<a name="line.768"></a>
<span class="sourceLineNo">769</span>      acquiredLockList.add(node);<a name="line.769"></a>
<span class="sourceLineNo">770</span>    }<a name="line.770"></a>
<span class="sourceLineNo">771</span>  }<a name="line.771"></a>
<span class="sourceLineNo">772</span><a name="line.772"></a>
<span class="sourceLineNo">773</span>  /**<a name="line.773"></a>
<span class="sourceLineNo">774</span>   * CycleDetectingLock implementations must call this method in a<a name="line.774"></a>
<span class="sourceLineNo">775</span>   * {@code finally} clause after any attempt to change the lock state,<a name="line.775"></a>
<span class="sourceLineNo">776</span>   * including both lock and unlock attempts. Failure to do so can result in<a name="line.776"></a>
<span class="sourceLineNo">777</span>   * corrupting the acquireLocks set.<a name="line.777"></a>
<span class="sourceLineNo">778</span>   */<a name="line.778"></a>
<span class="sourceLineNo">779</span>  private void lockStateChanged(CycleDetectingLock lock) {<a name="line.779"></a>
<span class="sourceLineNo">780</span>    if (!lock.isAcquiredByCurrentThread()) {<a name="line.780"></a>
<span class="sourceLineNo">781</span>      ArrayList&lt;LockGraphNode&gt; acquiredLockList = acquiredLocks.get();<a name="line.781"></a>
<span class="sourceLineNo">782</span>      LockGraphNode node = lock.getLockGraphNode();<a name="line.782"></a>
<span class="sourceLineNo">783</span>      // Iterate in reverse because locks are usually locked/unlocked in a<a name="line.783"></a>
<span class="sourceLineNo">784</span>      // LIFO order.<a name="line.784"></a>
<span class="sourceLineNo">785</span>      for (int i = acquiredLockList.size() - 1; i &gt;=0; i--) {<a name="line.785"></a>
<span class="sourceLineNo">786</span>        if (acquiredLockList.get(i) == node) {<a name="line.786"></a>
<span class="sourceLineNo">787</span>          acquiredLockList.remove(i);<a name="line.787"></a>
<span class="sourceLineNo">788</span>          break;<a name="line.788"></a>
<span class="sourceLineNo">789</span>        }<a name="line.789"></a>
<span class="sourceLineNo">790</span>      }<a name="line.790"></a>
<span class="sourceLineNo">791</span>    }<a name="line.791"></a>
<span class="sourceLineNo">792</span>  }<a name="line.792"></a>
<span class="sourceLineNo">793</span><a name="line.793"></a>
<span class="sourceLineNo">794</span>  final class CycleDetectingReentrantLock<a name="line.794"></a>
<span class="sourceLineNo">795</span>      extends ReentrantLock implements CycleDetectingLock {<a name="line.795"></a>
<span class="sourceLineNo">796</span><a name="line.796"></a>
<span class="sourceLineNo">797</span>    private final LockGraphNode lockGraphNode;<a name="line.797"></a>
<span class="sourceLineNo">798</span><a name="line.798"></a>
<span class="sourceLineNo">799</span>    private CycleDetectingReentrantLock(<a name="line.799"></a>
<span class="sourceLineNo">800</span>        LockGraphNode lockGraphNode, boolean fair) {<a name="line.800"></a>
<span class="sourceLineNo">801</span>      super(fair);<a name="line.801"></a>
<span class="sourceLineNo">802</span>      this.lockGraphNode = Preconditions.checkNotNull(lockGraphNode);<a name="line.802"></a>
<span class="sourceLineNo">803</span>    }<a name="line.803"></a>
<span class="sourceLineNo">804</span><a name="line.804"></a>
<span class="sourceLineNo">805</span>    ///// CycleDetectingLock methods. /////<a name="line.805"></a>
<span class="sourceLineNo">806</span><a name="line.806"></a>
<span class="sourceLineNo">807</span>    @Override<a name="line.807"></a>
<span class="sourceLineNo">808</span>    public LockGraphNode getLockGraphNode() {<a name="line.808"></a>
<span class="sourceLineNo">809</span>      return lockGraphNode;<a name="line.809"></a>
<span class="sourceLineNo">810</span>    }<a name="line.810"></a>
<span class="sourceLineNo">811</span><a name="line.811"></a>
<span class="sourceLineNo">812</span>    @Override<a name="line.812"></a>
<span class="sourceLineNo">813</span>    public boolean isAcquiredByCurrentThread() {<a name="line.813"></a>
<span class="sourceLineNo">814</span>      return isHeldByCurrentThread();<a name="line.814"></a>
<span class="sourceLineNo">815</span>    }<a name="line.815"></a>
<span class="sourceLineNo">816</span><a name="line.816"></a>
<span class="sourceLineNo">817</span>    ///// Overridden ReentrantLock methods. /////<a name="line.817"></a>
<span class="sourceLineNo">818</span><a name="line.818"></a>
<span class="sourceLineNo">819</span>    @Override<a name="line.819"></a>
<span class="sourceLineNo">820</span>    public void lock() {<a name="line.820"></a>
<span class="sourceLineNo">821</span>      aboutToAcquire(this);<a name="line.821"></a>
<span class="sourceLineNo">822</span>      try {<a name="line.822"></a>
<span class="sourceLineNo">823</span>        super.lock();<a name="line.823"></a>
<span class="sourceLineNo">824</span>      } finally {<a name="line.824"></a>
<span class="sourceLineNo">825</span>        lockStateChanged(this);<a name="line.825"></a>
<span class="sourceLineNo">826</span>      }<a name="line.826"></a>
<span class="sourceLineNo">827</span>    }<a name="line.827"></a>
<span class="sourceLineNo">828</span><a name="line.828"></a>
<span class="sourceLineNo">829</span>    @Override<a name="line.829"></a>
<span class="sourceLineNo">830</span>    public void lockInterruptibly() throws InterruptedException {<a name="line.830"></a>
<span class="sourceLineNo">831</span>      aboutToAcquire(this);<a name="line.831"></a>
<span class="sourceLineNo">832</span>      try {<a name="line.832"></a>
<span class="sourceLineNo">833</span>        super.lockInterruptibly();<a name="line.833"></a>
<span class="sourceLineNo">834</span>      } finally {<a name="line.834"></a>
<span class="sourceLineNo">835</span>        lockStateChanged(this);<a name="line.835"></a>
<span class="sourceLineNo">836</span>      }<a name="line.836"></a>
<span class="sourceLineNo">837</span>    }<a name="line.837"></a>
<span class="sourceLineNo">838</span><a name="line.838"></a>
<span class="sourceLineNo">839</span>    @Override<a name="line.839"></a>
<span class="sourceLineNo">840</span>    public boolean tryLock() {<a name="line.840"></a>
<span class="sourceLineNo">841</span>      aboutToAcquire(this);<a name="line.841"></a>
<span class="sourceLineNo">842</span>      try {<a name="line.842"></a>
<span class="sourceLineNo">843</span>        return super.tryLock();<a name="line.843"></a>
<span class="sourceLineNo">844</span>      } finally {<a name="line.844"></a>
<span class="sourceLineNo">845</span>        lockStateChanged(this);<a name="line.845"></a>
<span class="sourceLineNo">846</span>      }<a name="line.846"></a>
<span class="sourceLineNo">847</span>    }<a name="line.847"></a>
<span class="sourceLineNo">848</span><a name="line.848"></a>
<span class="sourceLineNo">849</span>    @Override<a name="line.849"></a>
<span class="sourceLineNo">850</span>    public boolean tryLock(long timeout, TimeUnit unit)<a name="line.850"></a>
<span class="sourceLineNo">851</span>        throws InterruptedException {<a name="line.851"></a>
<span class="sourceLineNo">852</span>      aboutToAcquire(this);<a name="line.852"></a>
<span class="sourceLineNo">853</span>      try {<a name="line.853"></a>
<span class="sourceLineNo">854</span>        return super.tryLock(timeout, unit);<a name="line.854"></a>
<span class="sourceLineNo">855</span>      } finally {<a name="line.855"></a>
<span class="sourceLineNo">856</span>        lockStateChanged(this);<a name="line.856"></a>
<span class="sourceLineNo">857</span>      }<a name="line.857"></a>
<span class="sourceLineNo">858</span>    }<a name="line.858"></a>
<span class="sourceLineNo">859</span><a name="line.859"></a>
<span class="sourceLineNo">860</span>    @Override<a name="line.860"></a>
<span class="sourceLineNo">861</span>    public void unlock() {<a name="line.861"></a>
<span class="sourceLineNo">862</span>      try {<a name="line.862"></a>
<span class="sourceLineNo">863</span>        super.unlock();<a name="line.863"></a>
<span class="sourceLineNo">864</span>      } finally {<a name="line.864"></a>
<span class="sourceLineNo">865</span>        lockStateChanged(this);<a name="line.865"></a>
<span class="sourceLineNo">866</span>      }<a name="line.866"></a>
<span class="sourceLineNo">867</span>    }<a name="line.867"></a>
<span class="sourceLineNo">868</span>  }<a name="line.868"></a>
<span class="sourceLineNo">869</span><a name="line.869"></a>
<span class="sourceLineNo">870</span>  final class CycleDetectingReentrantReadWriteLock<a name="line.870"></a>
<span class="sourceLineNo">871</span>      extends ReentrantReadWriteLock implements CycleDetectingLock {<a name="line.871"></a>
<span class="sourceLineNo">872</span><a name="line.872"></a>
<span class="sourceLineNo">873</span>    // These ReadLock/WriteLock implementations shadow those in the<a name="line.873"></a>
<span class="sourceLineNo">874</span>    // ReentrantReadWriteLock superclass. They are simply wrappers around the<a name="line.874"></a>
<span class="sourceLineNo">875</span>    // internal Sync object, so this is safe since the shadowed locks are never<a name="line.875"></a>
<span class="sourceLineNo">876</span>    // exposed or used.<a name="line.876"></a>
<span class="sourceLineNo">877</span>    private final CycleDetectingReentrantReadLock readLock;<a name="line.877"></a>
<span class="sourceLineNo">878</span>    private final CycleDetectingReentrantWriteLock writeLock;<a name="line.878"></a>
<span class="sourceLineNo">879</span><a name="line.879"></a>
<span class="sourceLineNo">880</span>    private final LockGraphNode lockGraphNode;<a name="line.880"></a>
<span class="sourceLineNo">881</span><a name="line.881"></a>
<span class="sourceLineNo">882</span>    private CycleDetectingReentrantReadWriteLock(<a name="line.882"></a>
<span class="sourceLineNo">883</span>        LockGraphNode lockGraphNode, boolean fair) {<a name="line.883"></a>
<span class="sourceLineNo">884</span>      super(fair);<a name="line.884"></a>
<span class="sourceLineNo">885</span>      this.readLock = new CycleDetectingReentrantReadLock(this);<a name="line.885"></a>
<span class="sourceLineNo">886</span>      this.writeLock = new CycleDetectingReentrantWriteLock(this);<a name="line.886"></a>
<span class="sourceLineNo">887</span>      this.lockGraphNode = Preconditions.checkNotNull(lockGraphNode);<a name="line.887"></a>
<span class="sourceLineNo">888</span>    }<a name="line.888"></a>
<span class="sourceLineNo">889</span><a name="line.889"></a>
<span class="sourceLineNo">890</span>    ///// Overridden ReentrantReadWriteLock methods. /////<a name="line.890"></a>
<span class="sourceLineNo">891</span><a name="line.891"></a>
<span class="sourceLineNo">892</span>    @Override<a name="line.892"></a>
<span class="sourceLineNo">893</span>    public ReadLock readLock() {<a name="line.893"></a>
<span class="sourceLineNo">894</span>      return readLock;<a name="line.894"></a>
<span class="sourceLineNo">895</span>    }<a name="line.895"></a>
<span class="sourceLineNo">896</span><a name="line.896"></a>
<span class="sourceLineNo">897</span>    @Override<a name="line.897"></a>
<span class="sourceLineNo">898</span>    public WriteLock writeLock() {<a name="line.898"></a>
<span class="sourceLineNo">899</span>      return writeLock;<a name="line.899"></a>
<span class="sourceLineNo">900</span>    }<a name="line.900"></a>
<span class="sourceLineNo">901</span><a name="line.901"></a>
<span class="sourceLineNo">902</span>    ///// CycleDetectingLock methods. /////<a name="line.902"></a>
<span class="sourceLineNo">903</span><a name="line.903"></a>
<span class="sourceLineNo">904</span>    @Override<a name="line.904"></a>
<span class="sourceLineNo">905</span>    public LockGraphNode getLockGraphNode() {<a name="line.905"></a>
<span class="sourceLineNo">906</span>      return lockGraphNode;<a name="line.906"></a>
<span class="sourceLineNo">907</span>    }<a name="line.907"></a>
<span class="sourceLineNo">908</span><a name="line.908"></a>
<span class="sourceLineNo">909</span>    @Override<a name="line.909"></a>
<span class="sourceLineNo">910</span>    public boolean isAcquiredByCurrentThread() {<a name="line.910"></a>
<span class="sourceLineNo">911</span>      return isWriteLockedByCurrentThread() || getReadHoldCount() &gt; 0;<a name="line.911"></a>
<span class="sourceLineNo">912</span>    }<a name="line.912"></a>
<span class="sourceLineNo">913</span>  }<a name="line.913"></a>
<span class="sourceLineNo">914</span><a name="line.914"></a>
<span class="sourceLineNo">915</span>  private class CycleDetectingReentrantReadLock<a name="line.915"></a>
<span class="sourceLineNo">916</span>      extends ReentrantReadWriteLock.ReadLock {<a name="line.916"></a>
<span class="sourceLineNo">917</span><a name="line.917"></a>
<span class="sourceLineNo">918</span>    final CycleDetectingReentrantReadWriteLock readWriteLock;<a name="line.918"></a>
<span class="sourceLineNo">919</span><a name="line.919"></a>
<span class="sourceLineNo">920</span>    CycleDetectingReentrantReadLock(<a name="line.920"></a>
<span class="sourceLineNo">921</span>        CycleDetectingReentrantReadWriteLock readWriteLock) {<a name="line.921"></a>
<span class="sourceLineNo">922</span>      super(readWriteLock);<a name="line.922"></a>
<span class="sourceLineNo">923</span>      this.readWriteLock = readWriteLock;<a name="line.923"></a>
<span class="sourceLineNo">924</span>    }<a name="line.924"></a>
<span class="sourceLineNo">925</span><a name="line.925"></a>
<span class="sourceLineNo">926</span>    @Override<a name="line.926"></a>
<span class="sourceLineNo">927</span>    public void lock() {<a name="line.927"></a>
<span class="sourceLineNo">928</span>      aboutToAcquire(readWriteLock);<a name="line.928"></a>
<span class="sourceLineNo">929</span>      try {<a name="line.929"></a>
<span class="sourceLineNo">930</span>        super.lock();<a name="line.930"></a>
<span class="sourceLineNo">931</span>      } finally {<a name="line.931"></a>
<span class="sourceLineNo">932</span>        lockStateChanged(readWriteLock);<a name="line.932"></a>
<span class="sourceLineNo">933</span>      }<a name="line.933"></a>
<span class="sourceLineNo">934</span>    }<a name="line.934"></a>
<span class="sourceLineNo">935</span><a name="line.935"></a>
<span class="sourceLineNo">936</span>    @Override<a name="line.936"></a>
<span class="sourceLineNo">937</span>    public void lockInterruptibly() throws InterruptedException {<a name="line.937"></a>
<span class="sourceLineNo">938</span>      aboutToAcquire(readWriteLock);<a name="line.938"></a>
<span class="sourceLineNo">939</span>      try {<a name="line.939"></a>
<span class="sourceLineNo">940</span>        super.lockInterruptibly();<a name="line.940"></a>
<span class="sourceLineNo">941</span>      } finally {<a name="line.941"></a>
<span class="sourceLineNo">942</span>        lockStateChanged(readWriteLock);<a name="line.942"></a>
<span class="sourceLineNo">943</span>      }<a name="line.943"></a>
<span class="sourceLineNo">944</span>    }<a name="line.944"></a>
<span class="sourceLineNo">945</span><a name="line.945"></a>
<span class="sourceLineNo">946</span>    @Override<a name="line.946"></a>
<span class="sourceLineNo">947</span>    public boolean tryLock() {<a name="line.947"></a>
<span class="sourceLineNo">948</span>      aboutToAcquire(readWriteLock);<a name="line.948"></a>
<span class="sourceLineNo">949</span>      try {<a name="line.949"></a>
<span class="sourceLineNo">950</span>        return super.tryLock();<a name="line.950"></a>
<span class="sourceLineNo">951</span>      } finally {<a name="line.951"></a>
<span class="sourceLineNo">952</span>        lockStateChanged(readWriteLock);<a name="line.952"></a>
<span class="sourceLineNo">953</span>      }<a name="line.953"></a>
<span class="sourceLineNo">954</span>    }<a name="line.954"></a>
<span class="sourceLineNo">955</span><a name="line.955"></a>
<span class="sourceLineNo">956</span>    @Override<a name="line.956"></a>
<span class="sourceLineNo">957</span>    public boolean tryLock(long timeout, TimeUnit unit)<a name="line.957"></a>
<span class="sourceLineNo">958</span>        throws InterruptedException {<a name="line.958"></a>
<span class="sourceLineNo">959</span>      aboutToAcquire(readWriteLock);<a name="line.959"></a>
<span class="sourceLineNo">960</span>      try {<a name="line.960"></a>
<span class="sourceLineNo">961</span>        return super.tryLock(timeout, unit);<a name="line.961"></a>
<span class="sourceLineNo">962</span>      } finally {<a name="line.962"></a>
<span class="sourceLineNo">963</span>        lockStateChanged(readWriteLock);<a name="line.963"></a>
<span class="sourceLineNo">964</span>      }<a name="line.964"></a>
<span class="sourceLineNo">965</span>    }<a name="line.965"></a>
<span class="sourceLineNo">966</span><a name="line.966"></a>
<span class="sourceLineNo">967</span>    @Override<a name="line.967"></a>
<span class="sourceLineNo">968</span>    public void unlock() {<a name="line.968"></a>
<span class="sourceLineNo">969</span>      try {<a name="line.969"></a>
<span class="sourceLineNo">970</span>        super.unlock();<a name="line.970"></a>
<span class="sourceLineNo">971</span>      } finally {<a name="line.971"></a>
<span class="sourceLineNo">972</span>        lockStateChanged(readWriteLock);<a name="line.972"></a>
<span class="sourceLineNo">973</span>      }<a name="line.973"></a>
<span class="sourceLineNo">974</span>    }<a name="line.974"></a>
<span class="sourceLineNo">975</span>  }<a name="line.975"></a>
<span class="sourceLineNo">976</span><a name="line.976"></a>
<span class="sourceLineNo">977</span>  private class CycleDetectingReentrantWriteLock<a name="line.977"></a>
<span class="sourceLineNo">978</span>      extends ReentrantReadWriteLock.WriteLock {<a name="line.978"></a>
<span class="sourceLineNo">979</span><a name="line.979"></a>
<span class="sourceLineNo">980</span>    final CycleDetectingReentrantReadWriteLock readWriteLock;<a name="line.980"></a>
<span class="sourceLineNo">981</span><a name="line.981"></a>
<span class="sourceLineNo">982</span>    CycleDetectingReentrantWriteLock(<a name="line.982"></a>
<span class="sourceLineNo">983</span>        CycleDetectingReentrantReadWriteLock readWriteLock) {<a name="line.983"></a>
<span class="sourceLineNo">984</span>      super(readWriteLock);<a name="line.984"></a>
<span class="sourceLineNo">985</span>      this.readWriteLock = readWriteLock;<a name="line.985"></a>
<span class="sourceLineNo">986</span>    }<a name="line.986"></a>
<span class="sourceLineNo">987</span><a name="line.987"></a>
<span class="sourceLineNo">988</span>    @Override<a name="line.988"></a>
<span class="sourceLineNo">989</span>    public void lock() {<a name="line.989"></a>
<span class="sourceLineNo">990</span>      aboutToAcquire(readWriteLock);<a name="line.990"></a>
<span class="sourceLineNo">991</span>      try {<a name="line.991"></a>
<span class="sourceLineNo">992</span>        super.lock();<a name="line.992"></a>
<span class="sourceLineNo">993</span>      } finally {<a name="line.993"></a>
<span class="sourceLineNo">994</span>        lockStateChanged(readWriteLock);<a name="line.994"></a>
<span class="sourceLineNo">995</span>      }<a name="line.995"></a>
<span class="sourceLineNo">996</span>    }<a name="line.996"></a>
<span class="sourceLineNo">997</span><a name="line.997"></a>
<span class="sourceLineNo">998</span>    @Override<a name="line.998"></a>
<span class="sourceLineNo">999</span>    public void lockInterruptibly() throws InterruptedException {<a name="line.999"></a>
<span class="sourceLineNo">1000</span>      aboutToAcquire(readWriteLock);<a name="line.1000"></a>
<span class="sourceLineNo">1001</span>      try {<a name="line.1001"></a>
<span class="sourceLineNo">1002</span>        super.lockInterruptibly();<a name="line.1002"></a>
<span class="sourceLineNo">1003</span>      } finally {<a name="line.1003"></a>
<span class="sourceLineNo">1004</span>        lockStateChanged(readWriteLock);<a name="line.1004"></a>
<span class="sourceLineNo">1005</span>      }<a name="line.1005"></a>
<span class="sourceLineNo">1006</span>    }<a name="line.1006"></a>
<span class="sourceLineNo">1007</span><a name="line.1007"></a>
<span class="sourceLineNo">1008</span>    @Override<a name="line.1008"></a>
<span class="sourceLineNo">1009</span>    public boolean tryLock() {<a name="line.1009"></a>
<span class="sourceLineNo">1010</span>      aboutToAcquire(readWriteLock);<a name="line.1010"></a>
<span class="sourceLineNo">1011</span>      try {<a name="line.1011"></a>
<span class="sourceLineNo">1012</span>        return super.tryLock();<a name="line.1012"></a>
<span class="sourceLineNo">1013</span>      } finally {<a name="line.1013"></a>
<span class="sourceLineNo">1014</span>        lockStateChanged(readWriteLock);<a name="line.1014"></a>
<span class="sourceLineNo">1015</span>      }<a name="line.1015"></a>
<span class="sourceLineNo">1016</span>    }<a name="line.1016"></a>
<span class="sourceLineNo">1017</span><a name="line.1017"></a>
<span class="sourceLineNo">1018</span>    @Override<a name="line.1018"></a>
<span class="sourceLineNo">1019</span>    public boolean tryLock(long timeout, TimeUnit unit)<a name="line.1019"></a>
<span class="sourceLineNo">1020</span>        throws InterruptedException {<a name="line.1020"></a>
<span class="sourceLineNo">1021</span>      aboutToAcquire(readWriteLock);<a name="line.1021"></a>
<span class="sourceLineNo">1022</span>      try {<a name="line.1022"></a>
<span class="sourceLineNo">1023</span>        return super.tryLock(timeout, unit);<a name="line.1023"></a>
<span class="sourceLineNo">1024</span>      } finally {<a name="line.1024"></a>
<span class="sourceLineNo">1025</span>        lockStateChanged(readWriteLock);<a name="line.1025"></a>
<span class="sourceLineNo">1026</span>      }<a name="line.1026"></a>
<span class="sourceLineNo">1027</span>    }<a name="line.1027"></a>
<span class="sourceLineNo">1028</span><a name="line.1028"></a>
<span class="sourceLineNo">1029</span>    @Override<a name="line.1029"></a>
<span class="sourceLineNo">1030</span>    public void unlock() {<a name="line.1030"></a>
<span class="sourceLineNo">1031</span>      try {<a name="line.1031"></a>
<span class="sourceLineNo">1032</span>        super.unlock();<a name="line.1032"></a>
<span class="sourceLineNo">1033</span>      } finally {<a name="line.1033"></a>
<span class="sourceLineNo">1034</span>        lockStateChanged(readWriteLock);<a name="line.1034"></a>
<span class="sourceLineNo">1035</span>      }<a name="line.1035"></a>
<span class="sourceLineNo">1036</span>    }<a name="line.1036"></a>
<span class="sourceLineNo">1037</span>  }<a name="line.1037"></a>
<span class="sourceLineNo">1038</span>}<a name="line.1038"></a>




























































</pre>
</div>
</body>
</html>
